It doesn't seem that strange?

You can drastically change the amount of fallout with materials and design decisions, so it's worth considering.

For example, tsar bomba was tested with a lead tamper instead of uranium; this reduced the yield, but also the fallout. The Ripple design has no tamper, was used in the last US airdrop test, and produces very little fallout compared to other designs.

A limited fallout design allows for occupation and/or resettlement after an attack, so it seems useful to consider.

Yes, yes, it didn't make a practical difference because MAD makes them all unusable.