I've been playing with Pro, so it's possible.
For me, it seems I could only pull off moves, such as Guile's Sonicboom, after holding back for a long time (the combo states you have to hold back, then push forward + punch [for somebody who doesn't know]), but I did achieve it after some practice, and from what I recall, a few of Guile's moves did require that motion.
So, I'd say either keep trying the combos in case you've been performing them incorrectly, and perhaps recalibrate your thumb pad because the combos are entirely possible.