Ok, it was not what I thought it was, not even close. The latest version of EE4 dequeued
jquery-form. You see it in their change set here. I think it has to do with that we both enqueue a third party library
jquery-validate but with different dependencies and when they dequeue
jquery-form it takes the dependencies with it so the proper scripts are not being loaded on the page which in turn stops the page from functioning correctly.
I do not see a simple solution other than commenting out their change in their code which I have done. The registrations seems to work fine now. I was able to submit one without any errors. Give it a test.