Here is what I think Larian is doing.
1. Your tadpole is definitely different, like an alpha male/female tadpole. Notice how yours essentially influences everyone else's whether friend or foe. So, yours is more powerful and therefore likely more a part of you.
2. Therefore, if you die, your tadpole dies with you.
3. Whithers restores you to the condition you were in before you died. So, if infected before you died, you are infected still. Your tadpole is essentially a part of you now. Therefore, if you are resurrected, it is too.
4. If you haven't been dead that long, a Revivify scroll can resurrect you and your tadpole without Whithers. Again, since you and the tadpole are more one, if you die it dies and if you res it does too.
