Gurley wasn't held back by the 49ers: he was held back by the coaching staff.
Gurley did only have 63 yard rushing, but it was on just 15 attempts (for a 4.2 yard average).
Brown had 65 yards rushing on 13 attempts for a 5.0 average.
Prior to the 49ers game Brown had been averaging fewer that 4 carries a game. If McVay stuck to that this game and Gurley got those extra 9 attempts he would have hit 100 yards (assuming he maintained that 4.2 average).
(And for the record: good call coach - let Gurley run up his stats when it matters.)
AlbaNY_Ram