There is a gym I go to where the signal always used to drop to 3G indoors.
A couple of days ago I turned on VoLTE capability on my S8+.
I have not yet experienced any actual VoLTE calls yet here in Raleigh (we are not in the list of initial VoLTE markets but we are a 5G upgrade location I believe), BUT something else good happened.
My phone roamed on LTE in the gym for the very first time I have ever seen it roam anywhere. In fact, it was on TMobile band 4 at 80 down and 28 up on Speed Test.
Evidently they will no longer drop to 3G, but will keep LTE, roaming if necessary to do so, in order to preserve the ability to do VoLTE.
It seems this gift is being given only to people who have phones upgraded to VoLTE.