A "glitch" that just happens to disproportionately target LGBT works. Uh huh.
It seems Amazon is taking lessons from the Canada Border Services Agency, which has for many years been notorious for disproportionately confiscating gay/lesbian erotica as "obscene" while allowing most straight erotica through. (Although to be fair, Lost Girls, which IIRC mostly depicts hetero situations, got delayed at our border for some time due to its rather hardcore nature.)