That seems like an odd mistake, so I sort of doubt it is one. Just premature.
Puck Pedia is reporting this is a one-way deal, one year at minimum salary of $775,000.
Dylan Gambrell is 26, and a right-shooting centre. Seems like less and less of a mistake already. He was a second-round pick of the Sharks back in 2016, and he's played there and in Ottawa for a total of 233 NHL games. He has 17 goals. Depth centre, then.
Ottawa had him last season at $950,000, a fairly normal salary for a centre who plays limited minutes – just a bit goosed from the depth wingers who aren't Ryan Reaves. He's got no offence, in fact he makes David Kämpf look gifted at generating scoring chances. His defence was better when he wasn't on the Sens, which is damning with faint praise. He has played about 12 minutes a game in most seasons because he plays PK, where he seems to be mildly gifted. Surprisingly, his faceoff percentage is not very good, hitting 50% only occasionally and resting at 46.5% last year. (This man should have been a defenceman.)
Depth players with more than replacement level skills at any one thing are hard to find, and the hardest is a 4C who can do something useful in the faceoff dot so you don't have to trot out John Tavares for every draw you think is important.
If he's meant to skate around with Reaves and then play PK, I guess that's fine. Not a real value add.