could it be that it needs a little spacer (instead of removing the glass)

[thirstyone]

It's quite strange to hear that the glass affects printing accuracy (at least it somehow works with resin). or it's the other way round, and it's the micro gap between the pcb and the glass that introduces inaccuracy?
May be, scaling the pcb would help to factor this out?

[TMaxElectronics]

Any distance between the LCD and the PCB will reduce the print quality. Its a simple geometry thing. The furter away the object to be exposed is from the mask the larger the area exposed by the light will be. I hope this drawing helps understand it a little:

The green PCB is the one without the glass and the red one with it in place. You can see that while the green one is exposed properly, the red one has lost so much definition that the two cones of light from the adjacent holes in the mask overlap. The best option would be to take a smaller light source, but thats not really possible with the existing printers.

Using the LCD with the glass in place works as well with the resin as with a pcb, just that the smalles feature size you can reproduce is made significantly worse.