Unable to join 1.21.1 realm on version 1.21

the changelog says users running 1.21 can still join realms running on 1.21.1 yet i cannot join my friend's realm on 1.21.
he can join on 1.21 , its just me who cant.

the menu says "you need to be on version 1.21.1 to join this realm"
the realm automatically updated to 1.21.1 even when it was opened on 1.21 exclusively

Steps to Reproduce:
1. open 1.21
2. go to realms menu
3. try to join 1.21.1 realm

Observed Results:
it doesnt work

Expected Results:
for it to work like it says it will

you want to know how to recreate it? open version 1.21 and try and join a realm. boom. theres your answer.