I don't really think that there was an issue with how "Trials and Tribble-ations" glossed over the difference. "We do not disucss it with outsiders."
It was ENT that decided that the reason had to be shown.
yeah but ds9 set the precedent that there was an in-universe acknowledgement of the visual difference between TOS klingons and TNG klingons..
i think it would have been better if they didn't. I've long felt that what T'Girl proposed would have been the best route to go.