I don’t see a big differentiation in the role of a wingback and fullback in either of our systems. Even in a 4-3-3, the fullback was given loads of attacking freedom and was our only wide outlet. Our wingback still is arguably the last defender on his side of the pitch even if he has centre backs covering him, they also have to cover our midfielders who in turn are higher up the pitch than they would be in a 4-3-3. Look at how far forward and involved Mendy gets for City, he isn’t playing a more defensive role by any means than Bellerin.
Carlos and Cafu were 2 of the best ever attacking wingbacks/fullbacks and were given so much leway they were often offside. Not only did they play behind 3 centre backs, they also had 2 holding midfielders in 2002 giving them more freedom to not defend.
Expecting that level from Bellerin isn’t happening. You have to compare him to his contemparies and the only attacking fullback offering more key passes per game I’ve found in the PL is Mendy. Kolasinac actually offers slighlty less key passes per game, 0.8 vs 0.9 and Moses/Alonso both deliver less key passes.
Now perhaps the quality of key passes isn’t as good as they aren’t translating into assists yet but he is producing chances even though he isn’t in form. But he has got 5 assists per season in the last 2 prior seasons playing as a fullback/wingback which is high for that position and he’s only 22. He is also one of the quickest with the most stamina in that position, which always counts for allot.
Maybe Chamberlain would have offered more as an attacking fullback. He didn’t want to play there though