I tested this but it's unclear to me what should happen with this changeset applied. I tested in Safari and preview__content seems to be the same in trunk.

There's no change on the screen because .block-editor-block-preview__content has an initial value visible for overflow, so its content is visible now. However, .block-editor-block-preview__content has a wrong size. Please check the size of .block-editor-block-preview__content in your browser inspector. It has 0px width and a smaller height than it's content. If you set overflow: hidden; to .block-editor-block-preview__content, its content will be invisible.

Why this is happening: For example, contentHeight is 100, and scale is 0.1. The height of .block-editor-block-preview__content would be 1px because the height is 100 * 0.1 and then transformed by scale(0.1), but it shouldn't. It should be 10px. What we have to scale is not the parent container but the child iframe.

I believe issues with Block Previews have been resolved, and we can close this PR.

Thanks again for contributing, @ixkaito!

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