A bit late to the party but some extra info for you.
I was debugging why I could not get the default addresses in the Magento
customer_save_after event, and I too was just getting falses...
This is because after save, the addresses are saved (of course) and assigned ID's, however the Customers address collection does not assign these new id's to the private "getByIds" array map inside of it.
As SimonSolutions eludes to, by reloading the customer Model the addresses are also reloaded, becasue they are loaded (not added then saved) the id map gets correctly populated.
There is some overhead in reloading the whole customer model though, I have found the following snippet works to reload just the address collection, thus reducing the reloading overhead.
this is an alternative for future searchers, Kudos still belongs to SimonSolutions for the origional answer of course but this may help others :
//assuming $customer is our customer model
//clear address collection
//note do not daisy chain this method as it does not return the customer object!
//getting default addresses now works!
$myDefaultBill = $address->getDefaultBillingAddress();