Presumably he thinks that experimenting with different players in those positions is more likely to lead to negative results than sticking with what he knows. He'd rather stick with the players who have trained for 6 months as wing backs in his system than try to convert different players to that position in a very short time.
It's not like there is an obvious answer to the problem. Playing Lucas/Bergiwjn there might give us more offensive power but would you trust them sliding around on the edge of our box? Tracking runners? Heading crosses away? Playing offside? In our situation a manager like Conte is always going to prioritise defensive stability and trust in the attacking players to win us the game rather than make the team unbalanced by making a forward play in defence. Those types of experiments normally happen in preseason or the early weeks of the season, not with 5 games to go.
Surely Kane and Son can notch a few goals and make the issues at wing-back irrelevant (in the short term)?
You say that, but how many games have we won with Sess and Royal or even either? Bet it's not many.
Our best run of form came with either or both of Doherty and Reguilon.