IWL12 and GWL08 are not HE machines, although IWL12 could be considered pseudo-HE. I don't think it can accurately be said that F&P "[does] not want" consumers to use fabric softener, being that all their machines have a softener dispenser of some ilk. Use in moderation, definitely. I have had some softener build-up on both machines in the base of the agitator and on the basket hub (direct line-of-fire where it dribbles when dispensing). I wouldn't call that a system-wide case of scrud or sludge as there were no significant deposits elsewhere. A "machine clean" hot soak cleared it some but not as well as I wanted, so I pulled the agitator and finished the job with a brush. When I use softener with the lint filter (which goes down into the agitator), there is noticeable softener residue (feels slippery/greasy) on the filter if I pull and clean it immediately after a load. I've never paid attention to how much of it would wash off during the next load if softener wasn't used.
The typical consumer may believe that softener falls into the "more is better" category, which it surely does not. Softener is typically dosed according to the load size ... as in physical mass of clothing. Frontloaders and HE toploaders deal with a higher concentration of softener by volume of water than do standard toploaders, so it seems reasonable that softener build-up may be more likely to occur. However, I'd expect more residue to occur in the dispenser tray and injection path to the tub than on the basket and tub themselves.
The typical consumer may believe that softener falls into the "more is better" category, which it surely does not. Softener is typically dosed according to the load size ... as in physical mass of clothing. Frontloaders and HE toploaders deal with a higher concentration of softener by volume of water than do standard toploaders, so it seems reasonable that softener build-up may be more likely to occur. However, I'd expect more residue to occur in the dispenser tray and injection path to the tub than on the basket and tub themselves.