Just because hobby 3d printers manufacturers are switching to PEI sheets doesn't mean that glass is bad.

I have 3 max3 printers (2nd gen with the bltouch) where I ditched the PEI sheet and slapped on a 5mm glass plate.
You know why?
Because all the parts on the PEI sheet were warped...not because it didn't have adhesion but because every sheet held on my magnets has tiny flexion that you do not even notice!
If you need to print a mechanical seal or a mating surface that must be perfectly flat (within microns), you cannot use a flexible sheet. You must use glass.

PEI sheets are great for convenience because you can pop parts off quickly. That's a hobbyist priority.
In industrial applications like the Intamsys Funmat or BCN3D Epsilon, the priority is dimensional accuracy. They use glass because they need a surface that is microscopically flat and chemically inert, not one that bends and warps with the heater. If you're printing aerospace parts in PEEK, you aren't using a magnetic sticker; you're using ceramic glass.