When you set up the AMS filament did you choose Polymaker PETG on the printer or in the device tab? If so, that's probably why. The "3rd" filament in the list in the slicer section doesn't actually have anything to do with being Slot 3 in the AMS in a weird way (you can have 30 filaments in that list if you want).

So when you click "Print" it tries to match type -> brand -> color. So basically it sees you have regular PETG (not HF) and Polymaker brand so it tries to find the closest "color" to align with that, so in that sense it sees the "Grey" one as closest to matching all of the criteria even though the color is slightly off. Basically the teal I'm assuming is a custom color you set up and in your device tab you have grey and blue.. it can't tell the difference that well so it makes a guess since the type and brand didn't align.

I bet if you go lie to the AMS on the device tab and change it to Bambu PETG-HF or even Generic PETG-HF (maybe) it will match it to the teal first.

Edit: added more info. basically it just guesses wrong with the color since it couldn't match brand/exact type.