Not sure if that is strictly true.
My local WEX got a delivery of 3 at launch and they sat about for ages, they were eventually sent back to Norfolk to fulfil other orders
They then got another 2 which also sat about for a while before being returned to Norfolk, my local WEX which is the only one in the country hasn't sold one yet and it's a very busy shop.
On the flip side they are selling tons of Canon R5's which is far and away there most popular camera body at the moment, lots of people who shot Canon previously and jumped to Sony are now jumping back.
Can't speak for other vendors as I only know about WEX as I am in there every few days but according our local Sony rep WEX are only getting them into stock in batches of 2 or 3 at a time and that is the reason they are always showing on backorder. They don't expect to sell them in huge quantities.
I can't make my mind up if I want one yet or not. Lots of pluses and negatives in the mean time I have just bought another 2 x A9's to tide me over while I make my mind up.