I got mine three days early Boatgirl - and I've been a 28 day cycle girl since I was 12. You could have set your watch by me.
Now, I'm not a doctor, but I know GLP1 affects your hypothalamus in your brain. The hypothalamus controls how hungry or full you are, how hot or cold you are, your breathing, your mood, and yes - your periods. I guess this medication makes the hypothalamus make more of the hunger blockers and more of the fullness hormones, and that might have an affect on the other hormones it's supposed to be making. Hence the late or early periods. I expect that would even out over time, as I know my doctor said that your body finds a balance after six-ish months. Your hunger does return, even when you stay on the medication, and that makes your eat more (but weirdly, your body does not put on weight). So if the hunger hormones even out, I expect the other ones do too.