I'd go 27:40s because of below:
Age is not a major issue - same age roughly as Farah was when he ran 28:15 on the roads in 2019 (I think Farah is a good comparison based on training history, events, performances, years at peak etc but Rupp not quite peaking as early) so would expect faster on track, and Rupp to be comparable.
2:09 in Atlanta worth approx 28 minutes flat on VDOT but considering that course, he likely was in faster shape
Has been doing speedwork for a reason as per previous posters
BUT
I can't see him having tapered dramatically for this if he is in marathon training so prob not deeper into the 27s