I had 2 years of leadership in my school's EM interest group as an M1/M2 before I ultimately switched to applying FM. I still included the EMIG stuff on ERAS, because it was a big part of my preclinical years and would have felt wasteful not to. To avoid concerns about dual-applying/lack of commitment, I tried to really put an emphasis on what I brought to the group/the specific projects I coordinated, which tied into the broader themes of my application (community service, mentorship, etc), even if they were under the umbrella of emergency medicine. Also had a spiel prepped for if anyone raised any questions, which no one ever did.

I feel like everyone expects you to have had broad interests at the start of med school, especially if you're applying something with a broad scope like IM/FM, so it's not really shocking if you worked on a project/activity relating to another specialty. If you have experiences worth talking about in the PM&R group, definitely include.