We ran into this when wife wanted to upgrade her 38 mm Hermes series 2, to a 44 mm Hermes series 5.
We have 3 38 mm Hermes bands that we thought would be useless.
We tried the 38 mm bands on the 44 mm case. They all fit perfectly. The double cuff looked better on the 44 mm case. However, the reverse was not true. 44 mm bands don’t look good on a smaller case. They lock fine, but the lugs stick out.
I don’t see any reason not to use 38mm and 40 mm bands on the 44 mm case.
They actually look better.