Laine isn't a defenseman, but for a winger he plays at least average defensive game, if not above average.
You don't get to play in team Finland if you don't know how to play your position in defensive end. It's a requirement for everyone, no exceptions.
Laine started being the last forward to leave defensive zone and being the first one back in Jets already, and developed as a two way player in jackets, to the point they were going to use him as #1 center starting the season that turned out to be his last in Columbus. Injuries ruined that.
The "defensive liability" moniker is just a result of years and years of ignorant posts, looking at some advanced stats to try and sell the narrative. He's no worse defensively than any other wingers who are offensively as productive as him. He's not a great defensive forward, but he backchecks and plays his defensive position in the D zone. Obviously his best attributes are in offense.
For Florida this would be a complete non issue, as they have centers who have played successfully with Laine before (Barkov, Lundell, Luostarinen) and all are known for their defensive game. The L-L-L line worked really well in 4 nations, and Laine/Barkov have played great together before and they are very good friends