Dropping Borosilicate glass mug I recently got a glass tea mug. It's has double wall construction with a vacuum insulation (advertised as such). I noticed on the label, it specifically mentioned it's made of borosilicate glass, and to "discard if dropped".

I understand the purpose of making it out of borosilicate glass (thermal expansion when adding hot tea). But what would be the reason for the directions to link the material to needing to discard the mug if dropped (and not cracked or broken)?

Does the fact that it's made of borosilicate mean it's structural or thermal properties might be compromised if it's dropped?
Pyrex glass labware can be dropped, scratched, even used if cracked (I've started filling a beaker, then noticing that there was a crack - but it still seemed OK).
Borosilicate glass for commercial (non-lab) use is often tempered, so that a scratch is a potential hazard - the item might fail unexpectedly. The issue is not so much the borosilicate but the tempering.