“.. suggests that the President is either mentally diminished or openly deceptive in such moments...”
Pathological liar/sociopath is what he is.
throughout his political life Biden has lied to enhance his resume, make himself look like a better person, or just to impress people. Now it’s hard to say if the dementia is the cause or his sociopathy? He may not even know where or when or why his son died he’s lied about it so long.