I understand it just overrides the lock, but what's funny is that everytime I install the ROM fresh, VoLTE is enabled only till first roboot, then no VoLTE anymore (unless unlocked via this code). I'm just saying that carrier settings seems to be there and it works once the lock is turned off
Just for your awareness, there's a way to enable both VoLTE and VoWIFI on MIUI V10 roms (xiaomi.eu included!).
Use these codes in the dialer:
I'm attaching aproof it works from the latest xiaomi.eu beta present on my Mix2s (polish carrier...