That’s a good question.
V1 is typically the most important tube in any tube amp as it sets up the whole preamp gain structure. If you swap out different V1 tubes I do find they make audible differences. So maybe it’s something like that?
I agree there is something nice about having a real tube circuit in the mix. Quite a few people do something similar with the Power Station but using it’s power amp after the modeller, Self-Attenuation mode: Can the Power Station add power tube mojo to my modeller or preamp?