Not to be argumentative, but he did not say he endorses Trump.
He said he assumes he will support him. There is a very big difference.
If he had said “yes” to that question you would be right.
He left wiggle room. The guy uses the very same legalese that the Clinton’s do. They’re always wiggle room, so they can claim they never did say what you think you heard them say.
Every politician uses wiggle-room words, including Trump; and Trump uses them more than most. That’s OK, it’s part of keeping your opponents off balance.