Just for you since you like to verify on that web site.
There is a type of nitrifying organism called
archaea which can operate at very low pH. The problem is that these organism are what are called obligative acidophiles. I.e. they ONLY work at low pH. These organisms also grow very slowly. A nitrifying bacteria might double in population every 24 hours under optimum conditions.
Archaea will double in population every ten days under optimum conditions.
Since this is a logarithmic relationship this is a huge difference. And there is no good way to increase the speed with which they grow. So an acid tank will need four to twenty four months to “cycle”.
So if one has an acid tank with low pH water one can simply cycle for four to twenty four months and the aquarium will then cycle ammonia, just like an aquarium above 6.5 pH.
Reference:
https://aquariumscience.org/index.php/2-12-beneficial-bacteria/
Edit - Very low pH for obligative acidophiles is 2-4. Won't happen in a normal aquarium.