It seems to me that this discussion is a between people who have most possibly never flown for one of the offshore majors and those who have most possibly been trained by one of them and have spent their whole flying careers in offshore O&G. Offshore flying these days is all about automation in very reliable large, twin-engine helicopters and requires little manual intervention so why require pilots to have years flying onshore SPVFR?
It would most certainly mean better flying skills and airmanship but is not necessary and many pilots with that background would quickly get bored with the monotony of offshore flying. The present system of recruiting young pilots straight from ab-initio training as co-pilots with PICUS and eventual captaincy seems to work well (in UK anyway).
I do feel that they have missed out on a fulfilling career as a helicopter pilot which has so many more exciting and rewarding opportunities.