His comments didn't "surface". They were made openly.
And nothing he said was opposed to Biden. He just said there's a lot more context than people realize and innocents who are being hurt. Biden himself has called for a more tactical approach than what they've done.
This is just the news trying to spice up Democratic politics because it's not as interesting as the Republican politics.
If you ignore rhetorical differences then the US, all European countries, Russia, India, and China have basically the same position about the situation - Hamas is a terrorist organization, Israel is right in wanting to get rid of them, but Israel doesn't have the right to murder everyone in Gaza to achieve that, and, even ignoring the moral aspect, trying to do so is even counterproductive for the long term security of not only Israel but the entire region.
But how things are said, and what things are said, influence the public perception of the events and exact positions of public officials, and when it comes to what someone as influential as the president of the US says, this can have a big impact on what happens next.
I bet you could tell your ass from a hole in the ground, but you seamlessly call the hole in the ground your ass because your actual ass is raw.
Edit: Biden is making moves to allow him to fund Israel completely black box. As if Pentagon black box isn't enough, he wants President to Israel, full closed door blackbox.
Why does Bernies career amount to him giving the correct answer, and then some deeper party goon gets the headlines, usually right before they use the moment to become a complete lobbyist dick sucking asshat?
Actually it's not wavering as much as a display of Obama's pragmatism. He doesn't have to play with geopolitics the way Biden does, and would admit it.