Looks joke this is a limitation to the hosted checkout pages for paypal advanced.
From the documentation:
on page 132:
NOTE: To enable line-item support, send an email from the Primary email address on
the account to email@example.com
Starting on page 40, is the section for customizing the hosted checkout pages, the sample images shows Subtotal and tax only, The customizing instructions don't show a way to show the item name and details.
I can see in our code that we are passing the values to paypal, So you will need to contact them to find out if it possible to display those values.