I see what you're saying, but the very fact that it was decided that interspecies offspring should be implied in the first place should indicate the parent tags were breaking from the site's usual rule of not implying species.
I maintain that those tags that don't imply a hybrid species tag are most likely either mistakes, or cases where there is no agreed upon hybrid tag, like draconequus-pony hybrids, dragonlings, and kirin-pony hybrids. (A small tangent to note, many of these do have tags made for them, but they're relatively small and currently unrecognized as species tags)
At the very least, I would point out that all interpecies offspring parent tag that has implications set up imply hybrid
, so at the very least that needs to implied.