I agree Tesla needs birds eye view in order to compete, but only because FSD parking is not coming any time soon. I disagree that it's a free byproduct - DNN don't see the surroundings in the way birds-eye-parking-assist do, so it requires additional software development. Stitching all the video, and especially filling-in front view with manipulated old images (since there is no front bumper camera) will not just take software development, QA, and maintenance, but also compute cycles. Of course, given FSD doesn't do much of the originally advertised functions, maybe it doesn't use up most of the hardware so those cycles might actually be almost free (only cost is electricity since the hardware is already there doing not much). As for customers, it's a consolation prize for spending $8,000 on a feature which has been in vaporware status for the last 4 years.
Birds eye view really should be a much cheaper option, or even free on cars at Model S/X/Roadster price range. Obviously it has nothing to do with Full Self Driving functionality - it is clearly intended for Full Manual Driving. It is no different than if Elon was to tie new games to FSD package to make it feel more worth the money (heck, you could argue games can be used during autonomous driving, so more related to FSD than birds-eye-view-parking-assist).