I tried to look up a picture to illustrate the width of the 2012 and 2013 sirrus forks (elite and below, at least, anyway) and couldn't find one, but the fork in the 2012 and 2013 elite is quite a different shape. It is much more like an inverted U versus an inverted V.
When the LBS put on the 38s, there was more clearance left on the Surrus than there was on my Jamis Coda with 32s, and that Coda fits 35s.
Would love to know what kind of Sirrus Wanderer is looking at!