I'm simultaneously surprised and not surprised that this exists (we buy washable paper towels and beeswax items and similar for reusability) but even I think that's even a bridge too far. More power to anyone who is using those products though.
I've personally always found US customs easy to deal with for purchased products. When we came back from France last year with around a case of wine my wife was worried and I'm like what is there to worry about? we're not smuggling anything and the worst case is we just pay a duty on the wine of a $1 or $2. You just declare it and if duties are applicable you just pay them. It always seemed to me they were really there to just keep people from doing crazy things or outright breaking import laws. Similar to your experience, coming back from Toronto with a few purchased items, US customs just did not care at all.