Even that is no longer the case in the modern NHL. Much better to have a defenseman who can take away a guy's stick than to be trying to plow each other out of the way. Positioning is leverage and leverage is very hard to overcome through strength, unless the disparity in strength is massive. Also, our defensemen are terrible at blocking shots and terrible at taking away shooting lanes with positioning. Neither of those things are attributes solely of the physical defenseman.
I'll also disagree on Brannstrom. His defensive positioning leaves a lot to be desired and he's often late to engage, which means he's already at a deficit in leverage. It's one of the main reasons he looks like he loses so many battles. He was late to arrive to the play and he's battling someone who established position and has leverage.
Sanderson is not some physical behemoth, he's not overly large and certainly not "heavy" in the classic sense. What makes him so damn successful is anticipating plays and engaging early. He's there at the time the puck arrives which means he's established, ready to battle and use leverage to his benefit.
Yes, big and strong helps a lot but only if guys have good positioning, good anticipation and good skating. It's why guys like J. Brown and Gudbranson are not stars in the league despite their size and strength advantages. And it's why the top top top defensemen in the league are guys like Makar, Josi, Fox, Hughes, Morrissey, etc. Not guys at the top of any list for big and strong.