I built a nether portal in spawn area, a droper drops item in the portal to keep spawn area loaded. And set a command block speaks "0".

Then I loaded 5*5 chunks in nether by using hopper.

I the center one of these chunks , I set two command blocks, one is powered by a minecart speaking "4", it's used to check whether the center chunk is entity loadable. Another one is powered by a comparator speaking "1", which is checking the carpets from over world.

Finally I found that the command blocks in nether didn't work.

which means 5*5 hopper loader can't load chunks a entity processing chunk.

It will broke such as iron farms and concrete farms, blablabla.

I hope it is a bug or I made some mistakes in preamble.

Seems hopper and nether portal can only load chunks for one tick?