Can it be appropriate to orient a 2x4 "wide side out"?
The reason why 2x4s are faced thin side out is:


The other way would mean you would use a 2x2 base which would be too wobbly, even for non-loadbearing walls.  
The wide side is more prone to warping issues.
Can you imagine trying to get plumbing/electric/whatever through the wall if it were framed like this.  
It is fine to have a board facing like this (given normally faced framing throughout) and is actually a must for an outside corner.


To your point exactly, what your are suggesting is much better than the alternative even given that you would have longer bolts.  The wide side will be much more stable against the concrete and will allow a tighter bond.