Interesting find! I am having troubles with the Working Profile Tone Response Curve function too in another thread: Bug with Working Space Tone Response Curve and bundled profiles
I played around with it a bit and it doesn’t disable highlight reconstruction, rather it messes with it. For example in this image, some highlights are clipped, and these are the highlight recovery settings (first screenshot) used. It does not recover all of the highlights so the clipping indicator tool is showing some black overlays. The TRC is set to none, as the second screenshot shows.
Now when I set the TRC to custom, and the values of gamma and slope are at the default 2.4 and 12.96 respectively, the highlight recovery actually gets a lot stronger such that the highlights are no longer clipped. It does not disable highlight reconstruction in all situations. Perhaps there is some other interactions where it causes that in your test images but not in this one of mine.
As noted in my other thread, the histogram changes also all across the tone range but it shouldn’t.