There must be at least a slight difference in meaning, but I guess it is not easy to evaluate what that word may have meant in its usual context 25 centuries ago.
What about the following line though:
if I compare with the words pada & paṭipada:
pada means "step, stride; footprint, trace, track, vestige, mark; a foot; footing, station, site, place;" so something somewhat static
paṭipada means "ingress, access, way, step, course, progress, practice, conduct;" something in motion
so its seems in that case, paṭi shifts slightly the meaning by adding the connotation of movement, evolution, progression, operation, being followed-up
if paṭi had the same meaning in paṭissati, it would probably shift the meaning to mean a followed-up sati, ie. operating, stable, steady sati, whereas just sati can also sometimes be weak and somewhat flickering
such an interpretation really seems to make sense in the context of mhstp (sati paccupaṭṭhitā hoti, yāvadeva ñāṇa·mattāya paṭissati·mattāya) since the purpose is indeed to get the sati to become strong and steady.