Rental vehicles only start a 9.3 lineups, but not uptiers for anything below that?

I’ve enjoyed using the rental or borrow vehicle feature that exists past 9.3, however I hadn’t been playing 8.7 or 9.0 lineups until recently, I had thought this feature existed for anyone uptiered to 9.7+ but it seems to only exist if you are in a 9.3+ lineup.

It was a nice flexibility feature to help give more players AA systems of the tier that might have missiles etc, but I don’t understand why a 8.7 or 9.0 lineup facing 9.7-10.0 uptier shouldn’t get to use it either?

Do I misunderstand how it works or is it only like a 0.3 br range? I was hoping say for a 9.0 japanese lineup uptiered to 10.0 would at least get to use their 9.3 AA as a backup spawn option.