This has been discussed here in several past threads and has been pretty well dismissed as a concern.
It has been pointed out in other threads that many high mileage oils intended for use in vehicles with catalytic converters, including some from SOPUS, have ZDDP levels that rival anything you'll find in current HDEOs.
Unless an engine is consuming a lot of oil, I don't think that there would be any problem since those adds that could poison a cat don't seem to volatize, judging by the residual amounts seen in UOAs.
Most of us take the cautionary note from RDS as CYA and the fact remains that these oils do carry current API SI certs. I can't think of any vehicles for which an API SM oil is recommended that don't have catalytic converters and Rotella, like every other dual rated HDEO is marketed as a mixed fleet oil.