He is kinda exaggerating a worst case scenario to proof a point..
Sounds like he's ony blaming MC or HC but the same goes for other dense leaved patches of low vegitation like mosses or just simple hard on impossible to reach nooks, crannies and cavities betweem and under hardscape elements. It all collects and accumulates dirt.
There aint much to proof that isn't already prooven, back in the day when water changes where considered a sin. A lot of unnecessary fish deaths prooved us wrong. Same story for an old time consensus that so called large self maintaning filter systems never needed cleaning, prooved us wrong for the excact same reason.
It is not a fact that dirty tanks cause diseases and disorders due to bacteria, the bacteria needs to be introduced in the first place. Some are rather common and all tanks have them, others are (or were) more rare and a role with the dice to get them or not. Hence some people never do a water change and never experienced a problem for years and some breeders never cleaned their large socalled self maintaining filter systems and aslo never experienced problems. Others follow these steps and it turns into a dissasters. This only prooves that the ones who didn't experience problems just got lucky with keeping the pathogenes out. Bad things can be introduced to our aqauriums in numerous ways, in ways which are impossible to detect with the naked eye till you diagnose diseases in your fish. The only fact is, if you are an unlucky one and you introduce something nasty, a dirty tank or filter has a higher risk of becomming a pathogene breeding box. History has prooven this often enough to make us realise that good husbandry and doing water changes is a necessity to keep closed system healthy and this changed the general consunsud about doing water changes. 30 years ago it was considered a sin, today it's considered a necessity. And still we encounter unlucky ones catching something nasty, go figure.
Anyway i'm not growing MC and i can pinpoint several hot spots in my tank i can not reach and definitively will collect dirt and it will do that as long as the tank is running. I guess this goes for 80% of all aqauscapes out there if not more.
I don't get it why this guy is making a storm in a glass of water or should i say aquarium, about Monte carlo collecting dirt.