Didn't say it was a bad thing. But if discussing what folks actually wear and carry for everyday self-defense, it's COS play. Although, I did see a young lady wearing a Wonder Woman dress in Whole Foods the other day.
If you can learn and practice useful skills in your outfit that translates from your high end 1911 38 Super to your J frame in your jeans pocket - ok with me. This is an old debate.
It is also under discussion in this thread, whether a COS play gun fighter outfit in a class like Spaulding's is useful. I wore my EDC rig of a Glock 19 and two spare mags under a cover garment.
Now for a carbine class, if you are training as someone who actually wears tactical gear (as I see LEOs in matches) vs. my friend who does carbine matches in a similar rig with a metal chest plate, etc. - Dave has a point. If the rig in class helps you to carry lots of mags to cut down on reloading time wasting, that's ok.