That seems like an impossible standard. What happens if the criminal took a job that payed less because of their criminal activity, put the legal paychecks into house payments, and the illegal money into food and other consumables?
Welcome to the debate on pretrial freezing of untainted assets. Some justices agreed with your point given the fungibility of money and all but the majority disagreed in https://en.m.wikipedia.org/wiki/Luis_v._United_States. The houses that were seized were probably not their primary residences and may be returned if they win at trial (they probably won’t given that they have nearly every major player in the indictment on tape acknowledging that they have received stolen property).