That was a strategy a few people mentioned a few years ago. Apparently within the last 5-10 years, the composition of toilet bowl wax rings has changed and some of them have components which may actually damage the graft unions.
It appears to me that the general issue is that newer formulations use more petroleum based products, whereas it used to contain more beeswax (which works great mixed with some other stuff).
Modeling clay seems to perform a similar duty without petroleum products damaging the wood.