In the situation you referenced (heel/toe), I think the call should be TD. It's not how they currently rule it, and I think you're very right about the inconsistency.

But here's my proposed solution: if anything touches down in bounds first (one foot, one knee, helmet, left elbow, right shoulder, ANYTHING) - as long is it's clear that the player touched down in-bounds first, then it's a catch. That eliminates any questions - either he touched down and there's green between him and the line, or he didn't.

But regardless, the current rule, as it currently is written, says that if any body part touches down in-bounds (other than the special weird rules involving the feet), then the second that happens, the catch is completed and it is in bounds. That's what happened in this case.