According to the article, they are in a different category:
They fall into two categories. First, Taft and Bush the elder. Both fell victim to an unusually strong third-party candidate -- Taft to Teddy Roosevelt and Bush to Ross Perot. Sans the extra competitor, it is almost certain that both Taft and Bush would have been re-elected.
I can’t comment on Taft since I wasn’t there. But GHWB only got a 3rd party challenger because he was such a bad president.