It is not on paper. Couple of ms ( 4ms ) is real, except it is not normal 5G but specific superset / version of 5G.
Your network needs to be End to End running on 5G-A ( 3GPP Rel 18 ) with full SA ( Stand Alone ) using NR ( New Radio ) only. Right now AFAIK only Mobile networks in China has managed to run that. ( Along with turning on VoNR ) Most other network are still behind in deployment and switching.
On that note, the BBC deployed a temporary 5G SA non-public-network to broadcast King Charles' Coronation, giving over 1Gbps uplink over 1km of the procession route.
More details are in the award-winning white paper linked from this[0] blog post.
Eh, I wouldn't be that surprised if it happens from time to time for big events. You'd be talking the very big sophisticated ones, but it is possible to get temporary licenses, and the equipment isn't _catastrophically_ expensive, particularly if you're just renting it.
This: https://en.wikipedia.org/wiki/Chaos_Communication_Congress usually has a temporary cell network (I think up to LTE last year) set up for the duration of the event, on a temporary license. And that's basically just done for fun.
Although the deployments are very limited, wouldn't the 5G mmWave coverage, in NFL stadiums for example, need to have both New Radio (NR) and Stand Alone (SA)? Or is there some bodge for down-rating your mmWave experience to a non-Stand Alone network? I understand you won't get SA end-to-end calling an endpoint on an LTE network, but, with 5G FWA also needing SA to achieve full performance, SA should be pretty widespread in the US, or is it?
Your network needs to be End to End running on 5G-A ( 3GPP Rel 18 ) with full SA ( Stand Alone ) using NR ( New Radio ) only. Right now AFAIK only Mobile networks in China has managed to run that. ( Along with turning on VoNR ) Most other network are still behind in deployment and switching.