That time a guy in Fresno told me to stop stretching carpet with my knees

So about 4 years back I was doing a 3 bedroom rental in Fresno, and the landlord's handyman was this old dude named Roy who just stood in the doorway watching me the whole time. I'm down on my knees pulling the carpet tight across the tack strip, doing that little knee walk thing we all do, and after like 10 minutes he goes 'son, you're gonna blow your knees out by 45 doing it like that'. I kind of brushed him off because I'd been installing for 6 years at that point and figured I knew what I was doing. But he walks over, grabs my knee kicker, and shows me how to set it with my hip and thigh instead of my knee joint, just one quick snap with the pad of my foot braced. Took me about 20 rooms to get the feel for it, but the stretch is tighter and my knees don't ache at night anymore. Roy passed away last year but I still think about that doorway moment every time I finish a bedroom. Any of you older installers switch your kick technique later in your career, or am I the only one who had to be told by a stranger?