I don't think so. We never rely on an astyanax serializer to produce a
simple number. Instead we manually wrap a SN constructor around whatever
RawSerializer returns.

I suppose we could change RawSerializer to do that, but we'd have to go
through and verify that RawSerializer is only ever used to deserialize
numbers that become SimpleNumbers.

Remember that time during the Astyanax cutover when I said that BF should
own all serialization?