For the last time (I hope), filmic highlights “reconstruction” is first and foremost aimed at ensuring smooth transition between area that will clipped at filmic’s output and non-clipped areas.
If you set filmic white clipping bound to the same clipping bound as the sensor, then both features may be equivalent (although they certainly don’t work the same).
But nobody says that filmic white exposure should always match the clipping threshold of the sensor “white” (first and foremost because sensors are RGB and know no white). So this highlight handling is completely contextual to what filmic does, regardless to the sensor dynamic range.
The usual highlight reconstruction happens much earlier in the pipe, on non-demosaiced data, and cares only about sensor bounds. Working on non-demosaiced data means it doesn’t see color, but arbitrary RGB plates with holes in them.
Thus these are not the same feature. They become equivalent, feature-wise, only if you willingly set filmic white exposure to the sensor scene-referred clipping value, which is a special case.