That has always been my take. Time in jump space has some variability so the tender wont know exactly to the minute when an x-boat will arrive, but the next boat and crew would be on ready status regardless. Once the expected boat arrives, any needed data begins transfer immediately. Once data transfer is complete and any needed physical cargo is transferred, the new boat can head out within hours if not minutes. I would assume a critical priority message can sometimes be the only data an x-boat would carry. It might not take more then a few minutes for a boat to jump in, flash a message to a tender that a Zhodani invasion has begun, and see a ready x-boat shove off to begin the next jump.Relays.
The X-Boat leaving the system need not necessarily be the same one that just jumped in.
I never thought a tender would be a small ship, but rather near to light cruiser size with repair, refueling, and replacement crew facilities and a fair number of small craft tied to it as well. I assume an x-boat tender would have a half dozen or more x-boats docked at any given time undergoing repairs, refueling, or on standby. Much like historical PT, destroyer or submarine tenders did during WW2.