Edit Jan 2, 2017: Well, it was a COPV bottle after all. There were buckles in some liners where super-cooled liquid oxygen pooled. From NASAspaceflight article, quoting the results of the investigation:
Each stage of Falcon 9 uses COPVs to store cold helium which is used
to maintain tank pressure, and each COPV consists of an aluminum inner
liner with a carbon overwrap. The recovered COPVs showed buckles in
their liners. Although buckles were not shown to burst a COPV on their
own, investigators concluded that super chilled LOX can pool in these
buckles under the overwrap.
When pressurized, oxygen pooled in this buckle can become trapped; in
turn, breaking fibers or friction can ignite the oxygen in the
overwrap, causing the COPV to fail. In addition, investigators
determined that the loading temperature of the helium was cold enough
to create solid oxygen (SOX), which exacerbates the possibility of
oxygen becoming trapped as well as the likelihood of friction
So, what follows has useful points, but leaned too much on a statement from another NSF article that sources were extremely doubtful the COPVs were the cause.
If by 'plausible' you mean that an exploding helium bottle could have caused an explosion like the one we saw, yes. However, the article's assertion that 'it is the most likely scenario' is not plausible.
It is always risky trying to get an accurate analysis of a very complex subject from a news source that isn't dedicated to that area. Gigantic explosions always get a lot of coverage, and a lot of news outlets have covered this that hardly ever mention space industry events. New Atlas reports on these kinds of things regularly, but there are several inaccuracies in the article. In response to the same update from SpaceX on the investigation, two of the top magazines dedicated to the space industry published long articles: NASA Space Flight and Space Flight 101. These articles use a bit of lingo so are somewhat harder for the general public to follow. Some googling might be needed, but not so much as to be onerous. Most of what follows is taken from them, with a few additional sources which are listed.
Here is what SpaceX's statement says:
At this stage of the investigation, preliminary review of the data and
debris suggests that a large breach in the cryogenic helium system of
the second stage liquid oxygen tank took place. [Updated 09/24: At
this time, the cause of the potential breach remains unknown.].
There are lines and connectors leading to the helium bottles, so a breach doesn't mean it was in the bottle. Also, because the bottles were being filled at the time, a breach doesn't mean the a piece failed, per se, in the sense that, if the problem was (for instance) that a pump in the ground equipment failed, it could have caused pressure waves to travel down the lines and into the bottles, pushing them beyond their design limits. In that case it isn't the 'fault' of the lines or the bottles.
Certainly because the helium bottles hold so much pressure, if one failed suddenly it could well look like the explosion that happened. The problem is, why would it do that. This is an important point.
The pressure vessels that hold the helium, the COPVs, have had problems in the past. They are spheres made of Kevlar embedded in a polymer, with a plastic or metal liner, that are filled with very cold helium gas up to a pressure of about 5500 psi. Failure of a strut holding one caused the loss of the CRS-7 vehicle when the COPV was thus breached.
That failure was during flight, when the structure is subjected to a lot of vibration and high acceleration. The helium vessel did not explode as a result, though it was at full pressure. In the AMOS-6 case, the COPVs had only been partially filled, and were not under any of the stresses that occur during launch. The NASA Space Flight article, says 'sources note they are extremely skeptical a COPV could be at fault, due to the amount of focus placed on them after the CRS-7 failure' - which is to say, because they'd lost a vehicle due to a breach in a COPV, they worked to make sure that wouldn't happen again. So, such a helium bottle exploding when it isn't even full, is under no extra g-force, and there is no vibration, would be very hard to explain. Something coming from elsewhere might have subjected such a bottle to excessive forces that led to a rupture in it (or in a line leading to it) but then the issue is that something, not the bottle itself.
In the CRS-7 flight, there was 0.9 seconds between the first indication of a problem and the loss of telemetry. In the AMOS-6 case, there was only 0.09 seconds between signs of a problem and the loss of telemetry. COPVs hold so much pressure that a massive rupture is like a small bomb going off, so it is awfully tempting to focus on them (and I have speculated a lot about it myself). However, there is a lot at stake in this investigation, and the FAA, NASA, and the Air Force are taking a much more active hand in it than they did last time. If the sources used by NASA Space Flight - and they get the best sources as the magazine is highly respected - say they are extremely skeptical a COPV caused this, then I am too.