Comment by pwg

This is most likely the reason. I could see a lot of "buy for me bot" users deciding that they really did not mean that color shirt (or some other reason) when they asked it to buy a "brand X shirt in size Y" and forgot to tell the bot what colors they would accept as options and did not realize the bot might buy an "electric purple" (or some other color they dislike) shirt because it was not constrained in color choice.