Custom Validation not working for login

Hello,

I try to apply this tutorial to a login page, to make it possible to login with phone number. But it only works on register forms but not on login forms.

https://docs.ultimatemember.com/article/94-apply-custom-validation-to-a-field

I tried to debug it with console logs, but on the login page the code will be never reached. Why can I apply this to register forms but not on login forms?

Thanks for this awesome plug in.