SCS did say that they were going to be working on rigid truck setups a few blog posts ago, I should imagine that this being in the base of one of the beta patches was a mistake - we saw the same thing a year or so ago when they accidentally left an AO texture for an MP4 side skirt in there :P
It is confirmation of what we're likely to see in the future, however doesn't tell us anything that we didn't know already!