Generally true, but it wasn't on the wheels that came on my Bike Friday. The hubs have 36 holes and the rims only had 24 so they had skipped every 3rd hole in the hub when lacing up the wheel.

If you're buying complete new wheels (i.e. hub, spokes, and rim together) then you can go with any spoke count - but a higher count (like 32 or 36) will usually be more durable and suited for heavier riders or those carrying touring loads while lower spoke counts will be favored by light riders and racers for the reduced air resistance and slightly lower weight.

But if you're just getting a new rim while keeping the current hub (and possibly spokes) then you should look for a rim with the same number of spoke holes as the old one so it'll be compatible with the hub (although there are some oddball combination like that on my Friday that can be made to work).