Drum Brake Springs

Many times the factory had a change from what was originally installed, to a replacement part that is different but functionally the same.

If on the other hand you have tried the replacement parts and they don't work, that's another thing.

BTW coil springs are just torsion springs. If the diameter is thicker but the length is longer it might have the same spring rate at a thinner and shorter bar.

In the same way a coil spring with 10 coils vs one with 15 but all other things the same, ( wire dia, coil dia) the one with more coils will be weaker. If you have another coil spring that has the same 10 coils but the wire dia is thicker it will be stiffer,
If you have another 10 coil spring same wire dia, but the coil diameter is larger the spring will be weaker.

These examples assume the metals in the springs are the same.

I only point this out to show that the shape of a spring does not dictate its properties.