Oh there’s no doubt they’ll take liberties with TLM story in the overall scheme of the show. But considering the timing of 306, airing not long after TLM is re-released on DVD/BluRay, they’re gonna potentially have new viewers who tune in just to see Ariel, so it’s good marketing sense to have her first ep showing iconic stuff from the original movie. “Surprise, she’s preggo with the future Captain Hook,” is likely to alienate any potential new viewers. Get ’em drawn into the show first, and then start messing with the story they know and love. Even leaving potential new viewers out of consideration, regular viewers would still probably prefer to see those iconic moments as the introduction to Once’s version, because we’ve been waiting so bloody long for Ariel to be on the show. Dunno how they could have her interact with the JR6 in present day, without revealing it if there’s some familial connection between Hook and Ariel right off the bat.