What problem does this address?

The new full-height button on the Cover Block adds a style attribute to the container, containing min-height: 100vh. This can only be overridden by Theme CSS with an unreliable [style="min-height:100vh"] selector.

The need for overriding the rule is e.g. in the event that the site has a header bar taking up e.g. 150px at the top of the page. Then, the first Cover Block would need to be min-height calc(100vh - 150px), so that the bottom edge of the Block isn't below the fold.

What is your proposed solution?

Apply the CSS rule through an appropriate CSS class name, which can then be overridden by the Theme CSS if necessary.