From #1629 (comment):

... if 'uncapturederror' simply never fires after device loss, which is probably ideal (and we should spec).

Editors think the spec should say that the uncapturederror event never fires after device loss. The reason for this is that, if it did, it could provide an alternate, but unreliable, signal that the device was lost. Applications which used that signal instead of the correct device.lost would at least sometimes fail to detect device loss. Additionally, it would be unclear to developers whether they have to listen to both signals, or if just device.lost is sufficient (it is).

I think this was part of the original design, for this reason, but we didn't write it into the spec. Unfortunately I don't see a note of this in ErrorHandling.md.