Bliot were described by the person who taught me the laws of kashrut as 'massless particle of taste that nevertheless have volume'. When (for example) you heat milk in a pot, even after you pour the milk out and wash the pot some bliot of milk remain,
I get into an argument each year with my rabbi when I cross off the line about selling the bliot in my pots. The argument point and counterpoint goes:
P) I couldn't deliver the bliot to him even if he wanted them.
C) If he wanted the bliot, he could just boil some water in the pot and he'd get some. If he kashered the pot and somehow kept all the water involved he'd get all of them.
P) Nobody wants the bliot anyway - it isn't anything useful.
C) A manufacturer can package something you want and something you don't want together and your choices are to buy both or neither - you don't get to split the products up.
P) Schmutz is not chametz, and bliot are even less than schmutz.
C) Jews love to be machmir on pesach - it is the custom to be stringent where possible.