First none of my post should be considered to be challenging you, just want to to make that point.
Second, while I've never seen anything by Meguiar's or any detailing company scratch glass there's a first time for anything. My background of detailing cars in Oregon and Washington led me to polish a lot of glass in my life due to a huge water spot problem in places where it rains a lot. So I have tried a lot of different products on glass by hand and machine and I've just never seen anything scratch glass because it is a very hard material.
It's possible to remove the scratches by polishing with the right products, Diamondite offers a Glass polishing kit and it says,
Diamondite® Glass Repair System Kit for Machine Application
I have not used this kit as I have a brand new windshield in my classic Jimmy.
You can also do some research on this forum by clicking to the search function and typing in the word,
cerium
Advanced Search Function
Note for best results with this kit or any kit you need a rotary buffer. If you don't have a rotary buffer you can get a cheapie at Harbor Freight or get a really nice one from AutoGeek here,
Car Buffers, Polishers and Pads
Just to note, you never need to let a compound dry, it adds no benefit to any portion of the process.
It's a mystery. Have you tried re-washing the windshield really well using a wash mitt and some car wash soap? Is it possible it's some type of residue?
My experience also. Didn't actually have much luck with any of the SMAT product to remove gunky films off glass either. Will they work? Yes. Are they good at it? Not in my opinion, I used M04 for decades as the size of the abrasive is large and chunky and that's what works best for removing topical films off the surface of glass.
Or the white colored UC filled in the swirls already there.
It's a mystery...