What problem does this address?

I have the feeling that the grow option for blocks and specially the spacer blocks is nearly unable to meet in the real world. Not from the UI but there are nearly no cases where the conditions are med to be able to use it.

I never give stacks a fixed height due to responsiveness of the layout.
The stack is a faulty way to achieve the goal.

The realistic setup is a columns block with multiple column. One column is stretching the space vertical based on the content. The other column has less content (CTA or Read-more-Link)and should be spaced out.

What is your proposed solution?

Enable the option "grow" for spacer blocks (or more) if they are direct children of a column block.
Maybe limited to columns that ate set to stretch the full height.

Alternative, but against this ticket main idea. Make stacks always grow to full height. Or give them an option to

That would enable a lot of great responsive layouts.