Every time I watch Falcon-9 moments like that at, I wonder:
Is it really intentional that the main engine of stage 2 after startup blows directly into stage 1´s top, maybe: in order to decelerate it?
Why would one risk damaging the booster which is planned to be reused? Is the energy saving so significant and the possible damage so irrelevant that it is a good idea? They could wait five seconds or so until the booster distanced itself a bit.
Because, if it is intentional, could it be that they put the booster at an angle first (how?) so that the main engine´s blow does not only decelerate but also support the turning of stage 2 so it heads further in the right direction for landing?
I mean, well, that´s quite a daring maneuver that needs great precision, especially the turn-moment achievement, no?