TomasHertlsRooster
Don’t say eye test when you mean points
I think this is mostly because all those players play inside a lot more than Thornton.
Quite possibly, but remember that xGF% accounts for shot location. A shot from the inside will provide a much higher "expected goal" value than a shot from the outside.
For reference, over the regular season for that time frame, Thornton has been on for 565 expected goals and 604 actual goals. And he's given up 432 expected goals and 431 actual goals. So, in the regular season, Thornton has demonstrated the ability to drive his actual goals above his expected goals. That makes a lot of sense because Thornton creates lateral movement prior to these shots that heavily increase the likelihood of a shot scoring without changing the "expected goal" value of it. But why isn't this present in the playoffs?
By comparison, Hertl, has been on for 245 expected goals and 240 actual goals. Couture, 391 expected goals and 376 actual goals. Burns, 611 expected goals and 622 actual goals. So, Thornton notably outperforms his expected goals while the rest of these guys don't.
Again, why does this change so much for Thornton in particular in the playoffs? I don't know. But I know that it has consistently done so over a long period of time and that's why I hold him accountable for the actual goals and don't give him a pass because his advanced stats are good.