A good argument, but it happens on Amazon when the search, research, and purchase were all on Amazon.

Yup, I get "buy it again" prompts on nearly all of my recent purchases, even when they are all durable goods that don't expire or require restocking, like say a tablet case.

Hmmm, that's really weird. It's probably an edge case that would be complicated to change in that case (never underestimate the power of inertia, especially in ML systems).

I feel like it might be almost trivially solved with a “buyer only needs one [for X months/years?]” property on the items.

It would likely have to be added by a human, but still: there are a relatively small number of items that people only need one of.

ML is pretty shitty at causal inference