Solidify vertex group not working properly (inconsistency)


I’ve come across a strange behavior for the solidify modifier.

As seen in this blend file, if there’s 2 solidify modifier on the same mesh and that each one is set to only work on it’s vertex group, the result is not what is expected.

It doesn’t work as gently as the bevel modifier does.

Is this a feature i don’t understand or is it really an inconsistency ? (compared to the behaviour of the bevel modifier).

Peace !

Exposed differently, why is it not possible to have 2 solidify with different thickness in one same object ?
why does it work so bad ?

While it works as expected for bevel.