It doesn’t matter if the Klingons, at the time of TMP, were intended to be a total retcon, because DS9 made lines of dialog that make that impossible
are you talking about Worf’s “we don’t talk about it with outsiders” line in Trials and Tribble-ations? Because I also think it’s ridiculous that people took that line so seriously. It’s a little meta joke in a comedic episode that solely exists to celebrate nostalgia for TOS. I don’t get how you can take it as serious confirmation that Klingon’s appearance changed in universe in that context.