But it's not the colloquial meaning, HDR is fairly well defined by e.g. ITU-R BT.2100, which addresses colorimetry, luminance and the corresponding transfer functions.
I think you may be operating with an idiosyncratic definition of "colloquial"
Colloquial meaning and the well defined meaning are two different things in most cases, right?
I don't think that's the colloquial meaning. If you asked 100 people on the street to describe HDR, I doubt a single person would bring up ITU-R BT.2100.