BART controlled the chance battle, drew it against Barzal, put up 2 goals in 6 (one of them big) which is more than meeting 4th line expectations, and if the overall stats look bad it's probably on the goaltending.
Also, if we're comparing them to Cullen, then
BART vs NYI SF/60 37.89 GF/60 2.11 xGF/60 2.49
Cullen/Kuhn in 16 and 17 SF/60 23.73 GF/60 1.65xGF/60 1.73
BART's stats with NYI roasted Cullen/Kuhnhackl's attacking stats in the cup runs (Cullen's individual numbers are all lower than BART's too).
There's no shift in approach. They're the same unit purpose as Cullen, only with better offence. They usually had the puck.
As for Staal-Cooke-Kennedy in 08-09 - a line that had a 30.77 GF%, or a -5 in 211 minutes if you want to express it that way - they too had
lower attacking stats than BART
I'm not married to ZAR-Blueger, but if we want to compare them to heroes of yore, I don't see a lot of room to criticise what they did - particularly from an offensive point of view.