[citation needed]
There's 20% more IM applicants for Endocrine than there are spots for the last 3-4 years with typically ~20 spots total unfilled in the match (and ~70 applicants who didn't match who would love those spots). Last year, Rheum had a full 50% more applicants than spots with <10 spots unfilled in the match.
I mean yes, ID has less applicants than spots (as does nephrology for example), but I've never heard of an ID fellowship accepting someone not IM trained, given that they wouldn't be eligible to take the boards. I suppose it's not impossible for that field, but otherwise I call bull**** on your assertion about scores of open rheum/endo spots that are willing to accept FM trained people.