What the Faulk
You'll know when you go
I think previously people had to fund their account and wait 5 business days for it to clear then be able to purchase it. Now they can just purchase immediately directly from their bank account.
I've definitely made instant purchases before (but with lower limits in the 3 digits, rising as you deposit more and go through various waiting periods) so I wonder if this was limited to certain banks or linked to a debit card or something else.