[Harris Azariel]

washing in that site reason is to avoid the growth of algae,fungi and any other microorganism that might grow on the media.but those things dont hurt ur plant.so washing isnt necessary.but if u wanna germinate seeds,i suggest u to sterilize it instead of washing it to avoid fungi or mould taking over the seeds.heres hw i sterilize my medium

-moist ur medium using distilled water(just moist it.no need to be wet.)
-after u moist it,put it in a wok or kettle or something like that and boil it until the medium dries or for 2mins++.
-then cool it down and u can use it.chances of growth of fungi/mould/algae is very low almost 0%

i use that method many times.try it.

Regards