Project treble is barely on 10% of all android phones. It's a step in the right direction that will take time to improve. This time next year should yield some meaningful results due to the obvious reason that phones shipped with oreo need to support treble.
Agree in theory that Project Treble should make rollouts of updates to phones and tablets faster because it is easier for the OEMs to update now that hardware specific code (the vendor interface -- at least with Oreo) sits in a separate layer beneath the rest of the operating system. The stuff in the vendor interface remains the same so there is no need to manually code it into the operating system each time. So far so good.
However, Project Treble addresses the phone/tablet's lower level software (the code written by the silicon manufacturers) and not designed for higher level UI changes and features many OEMs make. So these OEMs will still have to take the time with these latter changes.
Will these OEMs really then change their behaviour? I hope so.