I guess it depends on what you mean by "modern". My ~2003 Chorus 10 RD has no such screw, and I have seen as many Campag RDs without a B-screw equivalent as those that have one. My point being that many RDs function perfection well without a B-screw. It seems to me that if the large cog size and chain wrap are within spec for the RD, and the chain is the correct length, is there really a need for a B-screw?