That's actually important information. If the Velvet can't get NR CA with a Sprint SIM, but can with a TMo one, that does indicate that the S21 may have something similar going on. At which point I don't think it's a matter of TMo wanting one way or the other. Rather, Sprint's core can't do NR CA because n41 was going to be the only band.
I agree. What differentiates the Everything Data plan from kickstart except hotspot and unthrottled data?
As for 5g I can get NSA 5g on a sprint sim (tna) but cannot get SA 5g unless I TNX and get throttled to 2.3 on video... Crazy.
I would say given the Everything Data plan wording and the premium price paid for Everything Data, you should have unthrottled. If true, for me personally, this makes the purchase of any 5G phone from T-Mobile undesirable given that TNX is required to get 5G at all. Where I live inside the Columbus Ohio beltway, the speed ranking is Sprint, then AT&T, then T-Mobile, then Verizon. T-Mobile has improved, but not enough to change their ranking. T-Mobile would likely win if they converted one of the two Sprint only sites near me to T-Mobile (no permits seen).
The throttling should be validated against the physical network. What happens if only band b25 is allowed so it is only on Sprint even with the TNX network?