FWIW, the release notes for update 2019.8.2 mention the power increase. The release notes for 2019.5.15 did not.
Interestingly enough, 2019.8.2 also mentions some things that were already there previously, like sentry mode, dog mode, location folding mirrors.. and something else as well I think.
I just got it yesterday (it = 2019.8.2). Also interestingly enough (at least to me) is that I was not in early access program, but DID earn "priority updates" via the recently retired referral system. I have never gotten an update before this one in a manner which made me feel like I was getting something "early". I also decided to buy FSD for 2k recently to go with my already purchased with the vehicle enhanced autopilot. I have no idea if that combination of now being a FSD "owner" whatever that means, along with having "priority updates" (whatever THAT means), got me this update early.
I suspect its some combination of the two, but I did not have to accept any NDA or anything so...
Anyway, TL ; DR = 2019.8.2 specifically mentions the power increase in the release notes.