I agree. This video proves nothing. If it was Biden, the guards were merely outside of camera range when nobody else was around (though maybe poor procedure---which argues that it was not Biden). If it was not Biden, I didn't hear him claiming to be Biden or pretending to be Biden. It could have been just another dude with white hair. He sure seemed to walk with more balance and control than Biden.

Also, when and where was this supposed to have taken place. Too many videos without provenance.