This comparison isn’t exactly wrong, but it’s not quite right either. There’s a difference between “Greg specified this character uses this weapon, but didn’t explicitly say there weren’t others” and “Greg specified that this character has a weapon, but didn’t say what it was”.
The latter allows us to elaborate on a known weapon, while the former introduces something completely new.
It’s tricky to draw an objective line in the sand between the two, but I would place the division at “appearances”: giving Tuyet a shield (hypothetically) introduces a completely new item that has never been seen or referred to, while giving Orde a shield (before his Toa Tool was known) would simply be specifying the appearance of a tool that we already knew existed.
This isn’t a perfect rule (the Rhotuka Launcher that started this whole thing is still in the gray zone of this rule), but it at least gives some degree of objectivity.
(Also, TTV didn’t “press” Greg on their weapons, he gave that information voluntarily)