OK,got this part - this is referring to abusing the employees.

I read the former comment like that they are abusing/missusing the "technical Greencard mechanics" to get their employees past some checks/approvals/permissions/whatever or acquire whatever "special benefits" by working around whatever rules

It's pretty simple: you work as much as we tell you or we fire you. And good luck finding another job super fast with another company willing to sponsor a visa. This is the abuse. Plus, I think the pay is also not that great compared to US counterparts.