That makes a lot of sense to me. Pieces can be tremendously resourceful in defense when given sufficient thinking time, whereas pawns are easy to just push, and there's only so much thinking you can use with them ("cxd4 or exd4 ?").
Also high level play seems to be much about defending for a long time with few pieces (more or less assuming black will get behind the pawns at some point), and SF is much stronger than humans at that.
I have the feeling that SF with white basically sees that it's losing (e.g. like Stubenfisch said about "the lines humans invented to prevent Nxa4/xh4 ideas mostly lead in losing positions for white"), and tries to delay it most as it can, slowly becoming weaker and weaker, instead of rushing in, which would lose faster vs the perfect defense it sees for black, but would win more vs we imperfect human players.