This is nice in some ways but not nice in others.
Monk's whirling throw says nothing about breaking the grab or restrained conditioned on success.
In situations where the monk throws the target outside of the monk's natural reach, this is silly and should be reworded.
In situations where the monk throws the target to a location still adjacent to the monk, the grapple, pin could (and should, in my opinion) be maintained.
Also, for extra fun, can the monk throw the target 1 foot just for free extra damage?
