The Google Photos app is offering more insight into how the "Video Boost" feature on the Pixel 8 Pro will work.
tl;dr: they basically decompiled the latest APK of Google Photos and found these strings which give a few hints about how the "Video Boost" feature of the Pixel 8 Pro would work:
“To boost your videos, turn on backup in settings, or back up this individual video”
“To use Video Boost, you need to back up this video, which requires signing in with your Google Account”
“Waiting to back up video”
“Backing up for Video Boost. This may take some time. A notification will be sent when your video is ready.”
“Boosting video quality. This may take some time. A notification will be sent when your video is ready.”
“This may take some time depending on video length, internet speed, and battery status. A notification will be sent when your video is ready.”
“Boosting your video won’t affect your phone’s battery life or performance, but it may take some time. A notification will be sent when your video is ready.”
The boosted video could also be exported as a AVC or HEVC file according to the same decompilation.
Correct. I even believe the feature will not stay free forever. Google is accepting a small hit in terms of cloud costs to boost the Pixel 8 Pro sales right now. But IMO they will likely start to charge for that cloud work or at least put some quotas in place which you could increase if you pay (same as what happened to Google Colab), and at that point, if they're going to charge for it I don't see any reason why it would remain exclusive to the Pixel 8 Pro.