The unusually-placed rook on b4 still makes it difficult for Black to coordinate his pieces.
Of course, not to the active square f6 , when, after 16...Nf6 17.Nxf6+ Bxf6, White has tightened his grip on the dS-square as planned.
This was the intended destination. Not a surprise, as this is a regular pattern in such structures where both sides have advanced the rook pawn two squares.
Of course, here too Black was intending to exchange the foremost knight, before occupying e4 with the other one. Again, with all four minor pieces on the board, Black suffers some spatial problems; as seen previously, White may follow up with Ne5 and f2 -f3. The drawback is that the knight on b1 will be temporarily inactive (and in other cases, this drawback may just turn out to be too serious!), but here it may even assist the defense.