For the reason behind this, I'll quote u/french_panpan's comment in https://www.reddit.com/r/OculusQuest/comments/e978km/why_is_there_no_ptc_on_quest
"People who are anxious to try the new feature could access them (bug included) at an earlier date. That should be a low percentage of the users.
People who want the latest features would jump quickly on the new updates when they are branded "stable" by moving to PTC when the new version is officially released. That should be a higher percentage of users, but still low overall.
People who don't care will still get the slow roll-out.
And if something bad happens with the new version, people who voluntarily moved to PTC would be able to move out of PTC to rollback to the previous version. So it's actually safer that way."