I have noticed 2 things with this radio regarding 4G:
1. At my home, where 4G works great, when I switch from 3G to 4G via the phone settings, it takes longer than it did before to switch. Before, when I'd switch from "CDMA auto PRL" to "CDMA +LTE/EvDO auto" it would instantly shut off the 3G icon, then about 5 seconds later, the 4G-LTE icon would appear. Now, the 3G icon stays lit, for up to about 30 seconds, before it switches over. Everything still seems to work fine once that has occurred. It's a smoother transition, but seems to take a little longer for it to actually occur.
2. Yesterday, while at the grocery store (where I usually only get 1 or 2 bars of service and 4G data is spotty at best), I noticed that had switched over to 3G, whereas I hadn't on the old radio.
Both of these could explain why someone who was able to get 4G on the old radio, can't get it now. And I also agree it's probably a "good" thing if it's a case where the phone is defaulting to 3G sooner in areas with "fringe" 4G service.