So in SciCraft's ice farm, they have armor stands with frostwalker II enchantments to make the ice, but when I tried something similar I couldn't collect the ice later, is that a mechanic only in their version of minecraft? Or am I missing something?
They explain it fairly well. Ice forms next to other solid blocks. They got a pretty large surface there, so if it were set to freeze naturally, it would take forever.
Armor stands create strips of frosted ice in the water, moving slowly enough that some regular ice forms next to frosted ice.
Frosted ice melts back into water sources, but there are now a bunch of regular ice blocks 'seeded' in the water, next to which more ice can form faster.
If you wanna experiment, create a fairly large pool of water in a cold biome or high in the mountains. Time how long it takes for it to freeze completely. Now break all that ice, flood it with water again, and slowly move down the middle in frost walker boots. See how long it takes now