iPhones display LTE for some carriers here that are not fully supported by Apple for some reason. It is still full 4G, I have had Three and 48 and both had the same speed test results. Same thing was happening on Sky Mobile but they released a proper carrier file in an iOS update recently.
https://www.boards.ie/discussion/comment/122955796/#Comment_122955796
"I can see a few differences now that the update is installed. On unapproved carriers, it's possible to lock an iPhone on 2G or 3G, but those options are removed with official carriers. So the 2G and 3G options are now gone. Another one was that the Sky SIM would show 4G as LTE in the options, as well as beside the signal strength meter at the top of the screen, but it now shows as 4G, like most of the other networks do. The last one is that it now shows the network name as Sky IE in the network settings rather than Tele2 if the roaming mode on the SIM had ever been enabled. The LTE vs 4G one is a curious one for me, I think it's something to do with how American networks marketed their service. AT&T pushed Apple to display 4G for their 3G DC-HSPA service, so LTE meant that you were on true 4G. I saw someone on Virgin Mobile with an iPhone and that also displayed LTE like Sky did."
