Yep, and A/B testing as experienced by uninformed, unaware end-users is a dark pattern.
It undermines a perception of (and trust in) continuity which is necessary to make effective use of a tool. The best way I can describe it to the skeptical is: imagine the dials on your car's dashboard rearrange themselves occasionally overnight, and on some commutes to work you suddenly can't work the radio or the AC while moving at ≥35mph. Of course, since the widespread use of touchscreens, that example became very literal.
So the car manufacturer has figured out the "optimal" arrangement of dials and buttons on their dashboard for their preferred levels of user engagement. Great. How many of those users now associate their car's brand with inconsistency? "I can't trust the damn buttons to be in the same place the next time I drive."