@oliof @gloomyandy After discussing this with @dc42, I think I've misunderstood how extruder acceleration is limited under PA. The jerk / PA limit on acceleration is applied automatically by RRF, so the user doesn't need to set jerk or acceleration manually to take account of PA. The user sets extruder speed, jerk and acceleration at whatever the extruder can achieve in extruder-only moves (like retraction). The user only needs to know that acceleration is limited when PA is applied, to jerk / PA, so may have consequences such as slowing down or stuttering during printing moves, or skipping steps. This, at least, makes the documentation simpler! Which I'll now update, again...
Ian