Yes. Relying on fmt.Errorf and %w appear to be a more practical pattern when you don’t need to be able to match both the “inner” and “outer” type, which usually you don’t.

Also not sure the Is implementation is really to relevant. Nowadays, I would probably write a const string-based error with only an Error function, and rely on fmt.Errorf like you describe.

package mypkg
type strError string
func (err strError) Error() string {
    return string(err)
}
const (
    ErrFoo = strError("foo")
)