This seems plausible, but is the inverse of the traditional expectation of what grows and what stays the same. I refer only to a pragmatic experience of regex i

This seems plausible, but is the inverse of the traditional expectation of what grows and what stays the same. I refer only to a pragmatic experience of regex implementation (as opposed to a theoretical refutation of the point) - the size of the pattern is typically a constant and the metric of interest is usually the difficulty of scanning a fixed pattern over an arbitrary and increasing-sized input buffer with worst case input.