What's the difference between this and the film on the outside of an immersion chiller that "sanitizes in the boil" and makes your copper come out shiny? Recirc some hot wort through for a few minutes before you chill and it doesn't matter what's in there.
If you really care, make a hop stopper. I have and I never see any particulate come out when I backflush.
I think the difference is that with a plate chiller you have densely packed, angular surfaces that seem more likely to harbor hop/trub debris. That and you can't see what you're dealing with. I'm with you though in that if recirculating sanitizing boiling wort doesn't work, I'm hosed someday. Even with that and the fact that I backflush, flush and backflush again after every batch, I can help but worry a bit about what's jammed into the nooks and crannies. I get a lot of debris out of the chiller when I backflush.
Do you use your hop stopper with a pump? I have one but haven't used it thinking I'd clog it up by using my pump.
To the OP, I'll throw in two bucks if somebody wants to cross section their well used
chiller and post the results.