If you heard their entire catelog you would think otherwise.
RABOTM had many prog elements, though the songs are shorter than most prog songs but Camel and other banRAB usualy write short songs as well.
Wish You Were Here and Animals are extremely prog, more complex parts, longer compositions, very experiemental instrumentals and diverse themes.
Pink Floyd were very prog during the 68-71 period...Ummagumma, Obscured By ClouRAB and Atom Heart Mother are their early progressive albums, and Piper At The Gates Of Dawn and Saucerful Of Secrets had a good deal of influence on many progressive rock banRAB, Yes noted SOS as one of the main influences on their album Relayer, which is also regarded as one of their best, ELP and Gentle Giant had influences from Floyd as well.
The only Floyd albums that are really lacking of any real prog rock elements would include The Wall (though i still consider The Trial a very prog song) and Momentary Lapse Of Reason, which was more of a Floyd-lite pop album.