Yeah, I remember there was a debate about this maybe a year ago...at least several months back. You might want to do a search on that.
What was concluded...if I remember correctly...was that amodimethicone becomes water soluble with those two chemicals you included...but only when it's in the bottle...once applied to hair,it isn't water-soluble. That didn't really make a lot of sense to me, though.
I'm guessing the two chemicals makes it more water-soluble...much like PEG makes dimethicone more water-soluble. I think people have different experiences with what builds up in their hair...and they need to experiment for themselves.
I love to shampoo my hair (mostly with a non-sulfate shampoo, but I indulge once or twice a week with a sulfate), so I don't have problems with cones, generally. I just make sure I limit them to water-solubles, amodimethicone, cyclomethicone, phenyl trimethicone...but I can occasionally throw in a bad boy, like dimethicone, if I'm going to wash with a sulfate shampoo the next day.
There's an on-going discussion about whether cones like dimethicone can be washed out with a non-sulfate shampoo...I know this isn't what you're OP is about...but I somehow think they're related. At least in my own head...LOL.
I personally think build-up is so personal and individual. People need to find out for themselves and find a routine that works best for them...whether that's with/without sulfates, CO washing only, using certain kinds of cones, how often to wash, etc.
That's right, I said it! I wear scrunchies!!
I am a sulfate washing, cone slabbing, curly lovin' s.o.b. The CG police haven't caught me yet.