Many, many moons ago I dropped my GMT Master-II off at Rolex at St James Square they gave me a Tudor loaner (a Prince of some flavour, if my hazy memory serves).
It wasn’t a pristine watch by any stretch so I wasn’t overly worried about it. If they’re offering a loaner, provided you’re not abusing it, then I wouldn’t worry.
Quite a nice touch, turnaround was a few weeks and the whole lot cost ~£250. Those were the days.