I agree, Steve Mizerak, Jim Rempe, Alex Pagulayan and other pro pool players have all given pro snooker a go with little success. I also agree what you are saying about snooker players needing to have a bit of time under their belts playing pool to be really competitive in the tournaments, even the elite ones.
I played on the UK Pro 9-ball tour and also at the WC 9-ball qualifiers when it was played in Cardiff and the WC 8-ball qualifiers in Manchester and a lot of the established pool players had been snooker professionals previously who had not made the grade. For example, Darryl Peach, Majid, Mark Gray etc.
I also often came across and played inexperienced elite top 32 snooker players who just turned up to the events because they lived locally or to give them a crack.
These guys were just raw potting machines and were not as much of a handful as one might expect and I preferred drawing them over a well seasoned pool player because they had no idea of tactics, banks, jump shots and positional play.
I remember speaking to a Pro 9ball player called Steve Higton who was once a snooker pro who believed that a snooker player needed at least 2-3 years playing 9-ball etc to learn the game properly in order to be competitive and the elite players are not going to be able to put that amount of time into it unless they drop off the circuit.