That's not the case. In fact, friends + family start sending letters of intention to purchase (as binding as an AP&S (Agreement of Purchase and Sale) but not as detailed; typically locks in price and a vague description of units reserved for them) long before a building even has a height or sometimes even before land assembly. I've even seen letters as vague as "purchase 10 units at $N/sqft in next building within 5km of intersection X/Y".
Used to be that on the first day of sales while the front-door had the huge line of general public waiting to get in, the backdoor had a non-stop stream of agents converting their clients letters of intent+deposit and picking up their already pre-signed AP&S. Probably electronic delivery now since few even bother to build a sales office anymore.
The AP&S starts the construction count-down clock, but even it isn't dependent on approval.
In short, units can be effectively sold before the developer even knows they'll be constructing a building.
