Tz…, of course it applies to kollel. Making your parents pay money they cannot afford to is a mitzvah haba’ah be’aveirah. Stealing an animal and bringing a korban with it is no less a sin than forcing someone to pay money so you can learn. “Chamas”, extortion, is an aveirah too.
In general, there are 2 kinds of kollel learning- sustainable and unsustainable. Sustainable is when the wife has a parnassah that covers most of the bills, leaving a small, manageable amount for the parents or in-laws to chip in. This usually doesn’t bankrupt the parents or cause any parents to get into awful levels of debt. Unsustainable is having no income and expecting the parents and in-laws to provide everything. Between the large families and spiraling costs, this option is unaffordable for most.