I’ve wondered how much of a difference this actually makes. How often does a network get congested enough to impact MVNO users, but not congested enough to impact major carrier users as well?
If I do a speed test in the city square near me late at night, I'll easily pull >100Mbit on my phone. Utilization at like 3:00 AM is next to nothing. All the bars closed over an hour ago, there's nobody out and about but me coming home from a late night datacenter run.
I go to the same public square at 3:00 PM and I'll likely get 10-20Mbit. More than enough for most things I need, but definitely nowhere near what I was pulling at 3:00 AM. Friends with T-Mobile postpaid plans with me will probably still be able to pull ~100Mbit.
At big crowd events especially in places where there aren't usually as big of crowds (balloon festival, airshow, etc.) connections can be anywhere from okay to next to worthless. Maybe I'll get a megabit, but chances are even Signal might have to retry every now and then to send a text message.
I did a trial before we switched from a regular AT&T plan and I had significantly faster internet at my office, on the subway, and at home than with AT&T. The AT&T service was typically useless at sports games and concerts and stuff anyway, so the concept of deprioritization didn’t really phase me. Saved us $1000/year and we got better service. Couldn’t be happier.
I can confirm that an MVNO I was using in Tokyo barely worked during rush hour. It was like a 2g connection or worse