As sibling comments are pointing out, yes, any non-1.0 gamma (i.e. intensity^gamma) is a non-linear transformation, but what I think you are trying to point out

As sibling comments are pointing out, yes, any non-1.0 gamma (i.e. intensity^gamma) is a non-linear transformation, but what I think you are trying to point out instead (and is weird/unique) is that sRGB has a "non-constant gamma". Or, said another way, the non-linear intensity transformation cannot be represented by a simple gamma value. The transformation is, in fact, piecewise, with a linear transformation in the region from 0 to [some low intensity] and a more traditional gamma-like curve from [some low intensity] to 1.0. (In practice this curve is a pain, so many systems over the years have just settled to approximate it as a 2.2 gamma curve.)