Heard from FamilytreeDNA regarding calling Heteroplasmy as follows:

"Thank you for your email. Heteroplasmies are sometimes difficult to identify as
they can be subjective. Your sample has a small heteroplasmy at position 16090.
It is small enough that Dr. Behar, our chief mtDNA scientist, felt it could not
confidently be identified as a heteroplasmy as opposed to noise in the sequence,
and so he did not report it. We report heteroplasmies if at least a third of the
mtDNA has each result, as that is enough to distinguish the heteroplasmy from
noise. In your sequence the C is much stronger than the T."

So, as I read it, FamilytreeDNA will call a heteroplasmy only if there is a
minimum of a 33%/67% mix.

Sally