PCOS, Mirena, and period?

I've wondered this ever since I last saw my gyno, who thought it was strange. Is this really that strange? (She had no ill intentions about this btw, just oddly curious)

For background: I've been diagnosed with PCOS since ~2016 or so because I stopped getting my period and wasn't sexually active at the time. Since then, Ive lost ~50lbs (~22kg) naturally because I didn't want to start collecting more symptoms while I'm young. I sit around 190-205. Though not ideal for my height, I get much more mobility nowadays.

After other types of BC, I went with the Mirena that I'm now on the tail end of, but it's not quite ready to be replaced.

Flash forward to today, I still get spotting and/or a light period. I can't find a whole lot online about a period coming BACK while having both PCOS and an IUD. I'm not mad about it, nor worried. Gyno never seemed worried, either. Just curious has anyone experienced this?