When testing the file mol-timing-synchronization_svg.epub against EPUBCheck versions for EPUB 3.2 and EPUB 3.3, we are getting different results.

EPUBCheck (v.4.2.6) for EPUB 3.2 validates.

EPUBCheck (v.5.0.0-alpha-1) also validates.

EPUBCheck (v.5.0.0-beta-3) for EPUB 3.3 returns:
ERROR(CSS-030): /GitHub/epub-tests/tests/mol-timing-synchronization_svg.epub/EPUB/mobydick.svg(55,7): The package document declares media overlays styling class names but no CSS was found in the content document.

This error seems to come back regardless of how CSS is referenced in the SVG file. I tested it against:

• CSS directly added within a <style> element
• CSS file referenced via @import in the <style> element
• CSS file linked via the <link> element