Not sure about the pro, oneplus had a different team testing it, but the regular oneplus did have 5G working fine earlier this year I'm Visible, during their FUT. It's currently not working on the consumer build for me, but I'm sure it will be turned back on eventually. I'm still on a test build and test device
The pro does have better 5G but again, can't confirm if it was ever turned on, for Visible or not at this point
Note: my testing was through OnePlus not Visible and I don't work directly for OnePlus, but more independently for them through an FUT program
To turn on 5G on your OnePlus 8/pro or OnePlus 9/pro do the following:
1) Dial *#*#4636#*#*
2) Choose "Phone Information"
3) Under "Set Preferred Network Type:" choose "NR/LTE"
4) Enjoy your 5G connection!