It can still be pushed under the carpet past the origin even with how important it is.
There's no elephant in the room if Danny goes 'it's been ten years since I came out of made up kung fu dimension' and he doesn't follow up with saying how old he is after. Just....don't talk about it.
Also after a google search because things weren't adding up right, Danny was said to be 33 in IIF.
Which still is screwy for reasons other than aging the characters because if Danny is 19 when he leaves and the dimensions link up 'officially' ten years later, he should be 29