Do Blue Origin's BE-3 engines need to run for 7 seconds to “warm up”?

In the Blue Origin YouTube video Replay of New Shepard Mission 8 Livestream, "command engine start" is heard at T- 00:03, an audible "pop" can be heard at about T- 00:00.5 immediately followed by visible flames.

However, the apparent size of the hot exhaust and character of the sound continue to ramp until about T+ 00:06 and there is no vertical motion of the rocket until fully T+ 00:07.

Is there an almost 7 second "warm up" or ramping of New Shepard's BE-3 engine? Is this necessary function, or perhaps part of an exhaustive test (no pun intended) as this is a commercial space-tourism launch vehicle?

Video queued at T- 00:10

• Generally, liquid-fuel engines need a few seconds to stabilize after ignition. The engine is also monitored and the hold-downs are only released if the engine operates nominally. – Hobbes Apr 30 '18 at 7:21
• SSMEs had a ~6 second start sequence so this sounds reasonable to me. – Organic Marble Apr 30 '18 at 11:48
• Liquid engines have a highly tuned, extremely critical order of startup sequence. I think there's at least one question on the site about it, let me look. – Organic Marble Apr 30 '18 at 11:56
• space.stackexchange.com/questions/13095/… – Organic Marble Apr 30 '18 at 11:57
• For SSME I have a graph of chamber pressure vs time during startup which is essentially thrust. If you'd like to ask that question.... – Organic Marble Apr 30 '18 at 12:25