The issue is if the can’t meet their residency requirement there is no guarantee they will be able to move to Canada when they want to.
I think the residency can be easily maintained through 5 years, do the math:
You only need to be here 2 years out of 5 years, that means 730 days out of 1825 days
They could easily come for 6 months every year in the span of 4 years and would still maintain their residency...
Of course, given that they would be out of the country for 6 months each year, they would probably lose the provincial insurance every time they leave and would have to reapply from scratch when they come back, but since the person said their parents have so much money saved I guess a private insurance wouldn't be a big deal for them ?
In the end, if the person's parents don't want to come here at all then I don't see the point of sponsoring them but to each its own