Had me scratching my head too as with the lighter gauge it was spot on???

I did read somewhere that string thicknesses do affect the intonation and thus requiring string length to be adjusted which makes sense. It just requires a bit of experimentation in either direction to figure out which way is correcting the problem. Usually Flat means string needs shortening which is what I did on this baby, and yes remainder 3 other strings also required some fine adjustment too.

Edit: D'addarios are not cheap but these ones feel as smooth as for a set of round wounds so no chance of changing these in a hurry.