block__content div is omitted from preview when "Use Experience Builder for page templates in this theme." is enabled

Overview

In Olivero, when the user checks the "Use Experience Builder for page templates in this theme." in the theme settings the page markup is changed:

⬜️ Use Experience Builder for page templates in this theme not enabled:

<main role="main">
    <div class="region region--content grid-full layout--pass--content-medium" id="content">
        <div class="block block-system block-system-main-block" id="block-olivero-content">
            <div class="block__content">

            </div>
        </div>
    </div>
</main>

☑️ Use Experience Builder for page templates in this theme enabled:

<main class="site-main" role="main">
    <div class="region region--content grid-full layout--pass--content-medium" id="content">

    </div>
</main>

This has many nuanced and fairly complex ramifications particularly around styling (in Olivero the CSS is written in such a way that it assumes/requires that the .block-system-main-block div sits inside the layout--pass--content-medium div for example).

Proposed resolution

User interface changes