I think when people give advice, they are very cautious and tend to lean on the "safer" route for varied potential audiences. A new fish keeper may not know to wait until the cycle is complete to rinse their filter - I noted Jason said he waits about 4 weeks before rinsing his sponges in tap water. He also noted you would get more die off the longer you let the sponge stay in tap water. Some folks may not think about the potential risk for soaps, bleach, etc. in the sink area.
Also, everyone's water is different. I heard somewhere recently that sometimes municipal water can have significant spikes in chlorine due to some sort of "flush" to the system.
It's funny how many people interviewed on the aquarist podcast have memories of scrubbing down their entire tank, decorations, substrate, etc. with tap water because no one knew any better "back then".
I like Jason and watched his videos a lot when I got into fishkeeping. How smart of him to take his knowledge of science and bring his videos up a notch on the fish nerd scale. I think even seasoned aquarists would enjoy learning about the advanced science to this hobby.
Thanks for posting @Scott P.