we can do a head count of 12" clown loaches here. Like I said, probably less than a handful around. Sure there may be some that are not on the internet, but also many people overestimate the size of their clown loaches. 8-10" are seen every now and then, 12" are almost rare to non, and over 13-14" is extremely rare, even in the wild. Back in the days, there were 15-16" ones, that looked like giant carps.
As for hoarding, you could hoard all you want, if you keep it for 10 years, you may get it to a good 10-12 inches. They're not known for growing fast.
I have a clown that's around 8-9" , I've been growing it since march of 1990. lol I've only seen 1 in the 10-12" range.