Just had a nose around their site.
Not clear about what is a ticket and what is a voucher.
If you look at this link (refunds) it talks about both possibilities so its not clear
https://www.orlandoattractions.com/index.php?id=14
I think ATD will probbaly not match as this is really a US site with an added UK number.
A few months ago a thread on here debated how they might be breaking some of the Disney vendor rules by selling overseas. But they are also selling UK only tickets (21 day one) so they have access to this. Yes and about £5 cheaper. I am sure a cople of people noted that tickets arrived etc in fair time.
I will look for thread