This is technically true but a bit misleading. Sanders and Clinton had very different agendas on multi-trillion-dollar economic and foreign policy issues. The article you link states:

“The times that Mrs. Clinton and Mr. Sanders disagreed happened to be on some the biggest issues of the day, including measures on continuing the wars in Iraq and Afghanistan, an immigration reform bill and bank bailouts during the depths of the Great Recession”

Not to mention key proposals like Medicare for All where there is a steep divide between the young grassroots energy and the party leadership. I don’t think we should just paper over differences between the progressive and establishment wings of the party.

Sure, we should unite during a general election campaign against an extremely dangerous candidate (I voted for Biden & Harris in November and encouraged others to do so), but we are now in the middle of a governing year. It’s time to get things done, and we should hold our leaders (including the Biden/Harris admin) to account. Everyone should be vocal about the policies they support and put serious pressure on those who won’t act. To me, this is the whole purpose of democracy.