Sharks season ends in a week. Dahlen's season might end later. He's also unsigned (albeit qualified). It's impossible he plays in the NHL this year.
He's supposed to come over next year. I think his staying in Sweden this year wasn't really an issue - he had a bad first year in the AHL, went home to regain his form on a loan (perfectly understandable from the Sharks' perspective and they controlled his contract), dominated the league, and then covid happened. Dahlen stayed in Sweden and started this season there when there was no guarantee there'd even be an NHL season, let alone an AHL season - better to get in games that he could play than just sit around for sixteen months.
I don't know if he turns into anything at the NHL level, but his second season with Timra this year is more complicated than "he just wanted to play for his hometown team." Had he stayed there in the absence of covid, then that would be fair.