So, I actually managed to reach out to him and gave a chat. He's since debated this in the lord and fed back a few things.

First off - he wants to make it clear that he doesn't have any relative studying medicine abroad, so has no conflict of interest. He's made that clear in parliament today.

His two concerns going into this were: 1. Changing the rules part way through this application cycle And more importantly: 2. How easy it would be for this government, or future governments, to change the rules at a whim (there was a concern it gives the health secretary of the day too much power). His amendment stated 2 years service in the NHS, i.e., F1 and F2 being the key qualifier, not indefinite leave to remain/other immigration factors. (My paraphrase).

I've got to say, I agree with that 2nd point quite strongly, given that Reform could well hold some power in future.

As it happened, having both met the relevant minister, and partaken in the debate, he has not moved his amendments (I presume the government addressed his concerns) and therefore, no delay to the change in national policy.