I think part of my response got lost in the conversion. I had stated that conventional fishermen have an aversion to multi piece rods. I build a number of inshore flats spinning rods and almost always use 2 or 3 piece blanks. It is hard to convince some conventional guys that ferrules are not an issue. Usually I have to get them to cast one before they believe me.
So, to answer your question, that may be true for some of the heavier offshore or boat rods, but most spinning rods for inshore and freshwater are only slightly stouter than a comparable fly rod and the ferrules make no difference in the strength of the rod or the action. The best spinning rods I have built are on 3 piece GLoomis GL3 popping rod blanks, which have a stiffer butt than a fly rod, but about the same tip action. Everyone that has cast one loves it, but, unfortunately Gloomis quit selling blanks.