Maybe they will export the old customer data to the new platforms later so their old members can still log in using their credentials without creating a new account.
Most likely they are not going to. This was their previous statement
Unfortunately, we are not going to be exporting data from the old platform
and that means you would have to create a new account to access the new platform.
I mean there is no reason for them to export the data from the previous site on a later date. They could have done so before they rolled the site out if they intended to do so instead of asking players to make new account on the new site but it doesnt really makes any difference at all, it takes a minute to make a new one