Also, what kind of Common Core Math gives Biden a +8 advantage over Bernie in the primary, but has Biden losing to Trump and Bernie beating Trump? I can't think of how you could even cherry pick a sample to get results like that.
It is a stupid statement & can be easily explained by 1 or more of 3 things -
1. More GOP people cross over to Sanders - Unlikely. No Democrat has won 15-20% of the GOP vote in Decades & neither will Sanders or Biden.
2. Independents go for Sanders & Trump over Biden - Highly Likely. Even in 2020, in 70-80% of the states, Sanders has won more independents than Biden. This Sanders to Trump among Independents in the Mid-West was a common factor in 2016.
3. Many Sanders' supporters stay home - Also highly likely. 90K people voted Democratic downballot but chose not to vote for Clinton over Trump. Biden has no constituency & has the default electability vote while Sanders has a hardcore committed base & there will be a section of Bernie or Bust people.