They’ve said it’s accurate down to 0.001" (or, as you put it, 0.025mm) many, many times. That’s probably not a realistic number. IIRC, ~20" Mitutoyo calipers don’t even claim to be accurate down to a thousandth.
Really, with laser cutting, trying to get down to a thousandth is silly. The cut will frequently have a taper to it, and the taper alone can destroy any hopes of getting anything truly accurate to 0.001".
I think they’re talking about what I might call “positional accuracy” but is more correctly called “resolution”. (palmercr and I have argued about this terminology, and now that it’s probably at least a year later I’m finally willing to admit that he was right).
I’d say you’re probably doing pretty good if your cuts come out within 0.2mm (~0.008") from one side of the bed to the other, but I don’t have a Glowforge yet so this is only speculation.
I can’t recall anyone doing any extensive accuracy tests… or anyone even measuring anything larger than a few inches in length. Of course, many people on this forum could care less about “real” numbers and are content with whatever the marketing wankateers* have told them.
*credit to AvE