Generalizability vs. Transportability in Trials

Okay I will try to be very clear. There is on average a risk in each arm and on average a RD in each trial. This RD will vary from trial to trial based on each trials baseline risk (on average) because the RD is variation dependent. To avoid that a trial must deliver a variation independent effect (OR) from which we derive the clinically relevant RD based on our estimated patient related baseline risk. We are not talking about risk reduction here (which is a different ball game) but rather risk difference (RD). So I see no issues with absolute measures such as RD so long as they are computed properly. No one would report a RD alone in an RCT - it will always be paired with a relative effect measure and the RD, if reported, is applicable to patients like those in the trial only.