The suppression itself is what covers all four sites - TruthFinder.com, InstantCheckmate.com, Intelius.com, and USSearch.com are named on the page as the scope of the tool, so unlike most family opt-outs you're not relying on an inference about shared infrastructure. The Suppression Center's terms also reserve the right to discontinue the tool, which is not a reason to wait.
Classmates.com is explicitly excluded. It holds yearbook photographs and school records - the subject of most of the litigation against this company - and needs its own removal process on its own site. If an old school photo is what brought you here, the Suppression Center won't help at all.
Neither are the wider filings. Intelius, LLC's California data-broker filing alone lists twenty-two domains, several of which look like unrelated public-records sites - zabasearch.com, addresses.com, publicrecords.com, publicrecords360.com, peoplelookup.com, onlinesearches.com, courtreference.com, arrestrecordsearch.com, criminalrecords.com. Nothing states that suppression reaches those. Search yourself on the ones you recognise, and if you find a record, use that site's own removal route.