By this logic

if I work in an electronics store and sell, say, GPS units, I am only qualified to sell the brand that I use, not the one that might be best suited for each particular customer I encounter?

I cannot have used or tried them all. It’s not possible for one store to stock them all. However, I should have studied the specifications and reviews of those that I sell, and I should be aware of how they compare to one another. That will be sufficient.

The problem with many MLMs is that they only deal in one product line that provides any sort of profit margin for the IBO. Any others they carry often have very little profit associated with them and virtually no credit toward business volume. So the best you, as an IBO, can hope for is a decent price at the “discounted” IBO cost.

But then you aren’t really selling anything, are you? You can’t generate a profit if you only sell to yourself.