I suspect I am still missing your point, Manfred, so please bear with me.
The starting point (in camera) was to expose for the sky on the basis that the shadows could be brought up, whereas burnt out or clipped whites would be near unrecoverable.
Would you (as starting point in post) set the Shadows slider to 100 and rein it back a little to taste? As you say, the contrast would reduce; so I sought to remedy that in part by adjusting the Blacks and Whites.
I avoided changing the Contrast slider partly because that would have impacted the Blacks and Whites and partly because the objective was to only change the Shadows and Highlights sliders. I avoided changing the Exposure slider for the same reason.
It now occurs to me that you may have meant for me to use the Shadows/Highlights sliders in Lightroom before editing and blending in Photoshop, as before; but I took your suggestion to imply that the adjustments would only be made in Lightroom.
As you can probably tell, I am bit muddled in my thinking on this.