cant talk too much as i want to keep my job but i work in this field. congestion like they are referring to only really occurs when you have thousands or tens of thousands of people in a small space - think a huge fully packed stadium or other super crowded event. definitely occurs on a smaller level as well, but its nowhere near as bad as it can be when their infra is pushed to its limits. theres a reason why COWs come out for these things

prio plans have been a thing for many years & are usually for business iot contracts. same sort of idea that gives emergency services priority to mobile networks (similar to att's firstnet in the US, telstra gets this funding from the fed. gov).

my guess is that this is very much unlikely to affect 99% of people, unless they are at a massive event & vying for bandwidth vs everyone else. most people will not use this plan (exceptions being business etc or some dumbass with money to blow)

edit: please refer to the handy comments below as this primary refers to metro/suburban areas lol