Coming from a working class / poor background it absolutely is true. Until I graduated and working in a wealthy area with upper middle class background people, I had never heard of anyone having their parents pay for their house. This is really split based on how Wealthy your background is.

In North America its often considered "crippling" children to give them too much help. I've seen it repeatedly, with some families giving children 3 months after graduation to begin paying rent.

Everything from parents kicking their kids out or charging them rent at 18 (or ever) to anecdotes from North American friends of how they got pushed out of home to pay rent while in university.

The endless lectures of Dave Ramsey on not wanting to provide a "hammock" for kids are also an abundant source of information.

North American parents won't consistently have a college fund for their kids. Also planning to pay for the down payment on their home is absolutely not normal for them.