The 2018 video is him making the point of "Paul Ryan is right, to pay for these ridiculous tax cuts, you'd have to cut social security"
I'm also just really confused at the disconnect between Bernie's camp and Bernie himself. All of Bernie's paid staffers are going after Biden but Bernie himself kind of refuses to do so at all? What is the plan here?
But after that Biden goes on to say
'Now, Paul Ryan is right, we do need to cut Social Security and Medicare'
And suggests cuts based on income levels. He then goes on to list a bunch of stuff he'd do such as
progressive taxation overhaul and says
'And then you raise enough Revenue that Social Security can stay. With adjustments, but it can stay.'
Adjustments is Washington lingos for cuts. His own proposal, to reduce support based on income rates, is by definition cutting those programs.
It's incredibly hard to credibly divorce Bidens earlier statements to suggest that he wasn't in favor of the proposal to cut those programs. This is consistent with his position for decades.