If you are referring to the original A&A (Classic), then I don’t think that was the rule. You could always load/unload in the same turn, to my knowledge.
And leaving that DST alive and the Suez open invites another problem…
A pretty nice UK fleet roaming the Indian Ocean. By UK2 it can be 2 DST’s, an AC, 2 FIGs, 2 TRNs and a sub. That puts them on par with Japan’s remaining fleet after Pearl…