I think that was the first time someone actually acknowledged the change. And then there was a short arc on Enterprise providing an in-universe reason for that change.
Never actually watched Enterprise (yet) so don’t know the cannon reason they gave but re: first mentioned, yes it was, and I think Worf, when asked why Klingons looked different said something akin to “we don’t talk about it”.
Brow ridge change came up in the Tribble episode of DS9 too
I think that was the first time someone actually acknowledged the change. And then there was a short arc on Enterprise providing an in-universe reason for that change.
Never actually watched Enterprise (yet) so don’t know the cannon reason they gave but re: first mentioned, yes it was, and I think Worf, when asked why Klingons looked different said something akin to “we don’t talk about it”.
O’Brien: What happened? Some kind genetic engineering?
Doctor Bashir: A viral mutation?
The writers of Enterprise watched this episode and said, “yes.”