as far as a know, the HDR support comes from the scopes feature and Lumetri pops open a new HDR adjustment. As to if it will recover highlights that aren’t there, I don’t think so.
HDR is similar to RAW as it has whites and blacks that can be recovered. If you didn’t record in HDR or RAW, you won’t magically get recovered although the tool may work similary to the effect called Shadow/highlight which makes a more pleasant looking gamma adjustment than curves.