Let's make sure we are talking apples to apples here. The access priority for a user on a carrier's network is called QCI as explained here:
Quality of Service Class Identifier.
US Mobile's contract does have the higher QCI 8 priority, but only for the Verizon (i.e., WARP) 5G network as discussed here:
Priority Data on WARP 5G. USM's other carrier services T-Mobile (Light Speed) and AT&T (Dark Star) do not have QCI 8 Priority Data.
The problem with generic populist forums and social media like Reddit is that the bulk of the posters are not technically astute, unlike the typical BITOG member. Most of the info on Reddit is hearsay, supposition or anecdotal, not scientifically based. I doubt the average Reddit poster understands the difference between cell network priority versus cell tower saturation/overload. Just because you have high network priority, it doesn't mean that you will always be able to stream data during times of high congestion like at an NFL game venue or Taylor Swift concert. When a tower(s) reaches its maximum capacity, it won't allow additional user access, regardless of QCI rating. I look at it this way: Louis Hamilton can be in his Ferrari and me in my Honda; however, neither of us are going to get home any faster if the tractor trailer has overturned on the freeway.
With that said, here is a
2024 Reddit Thread where the poster does appear to have valid information on data prioritization.