There are a massive number of Nissan leaf's on the market, roughly 700 on trademe... mostly fresh imports (seems less than 10% have number plates on).
In Q3 2018 there were 637 leaf registrations. That means the market has about four months of stock on hand. I can see why some are getting the feeling the market is crowded.
Regarding the thing about government incentives, there is some risk to dealers that the incentive could devalue their stock on hand. for example if a $7k rebate was given to dealers when used leaf's left the port, then any further leaf's would undercut those already on the market....
The incentive should go to the buyer rather than the dealer, that’s the way it works in other countries. That way you get maximum visibility of the incentive by the public and you can credit the cars already here.