Like most others we’ve always laundered the sheets and towels where time permits, and explicitly explain why we haven’t if on the very rare occasions we were unable to.
This has evolved for us over past 3 years, going from mainly international sits to domestic sits. Now that we have a base again, we take our bed linen, duvet, pillows and towels with us which does take that pressure off the last day, and has made it more relaxing.
Of course this won’t be possible when we house sit overseas again. We’ve had a few sits in Mexico and central Amercia where we were told not to worry as the cleaner would sort, in which case we do still always strip the beds. But, I think, like @ScrewTheAverage, if there’s something that’s important to you, mention it, we wouldn’t be offended, we love as much clarity and clear communication as possible