That’s an implementation detail. The money - which wouldn’t be much - would be tied to them not coming here illegally again. There could be severe penalties for coming here illegally again, as there is for those who are deported.
maybe if the money was delayed .. for several years conditional on them not returning during that time with accompanying proof that they are indeed now living and have been living in their countries of birth.
Because otherwise ... they will get the money, and then either immediately return and be here AND have the money, OR a democrat or RINO president after Trump will just allow them to return, make them citizens AND let them keep the money!