I think this is one of best exaple where optional rule can be aplied.
If a young child runs up to the party and says "My mum says Mystra is the goddess of the weave... What's the Weave?" There is no possibility that Gale will not have an answer to give - but it is possible that someone else might not know much about magic and may not be able to answer this (still unlikely but possible). Because at least one character might fail this check, the roll must be made regardless, but the Dc is low enough that most folks can't reasonably fail it - Gale certainly can't. With critical failures on skill checks, however, Gale CAN fail to answer this question, and that just doesn't compute.
I thought this is the reason we have those not-rolled dialogue options. O_o
You know ...
[Druid], [Fighter], ... but also [Drow], [Baldurian], etc ...
I mean PC game is explicit environment after all ...
We are unable to get into any unimplemented dialogue situation ... and while possibilities can be (and sometimes are) oversighted ...
We get this unfailable options for our unfailable situations ...
So in your exaple Gale would (or should) have options:
[Wizard] Weave is just other word for Magic.
[Insert skill here] *try to explain it as thoroughly as possible ... yet easily so that kid understands*
