If the items featured the Global Shipping Program, the seller would not have been able to send a combuned invoice or indeed to combine the purchases.
Some sellers have settings for dealing with the sales process so that UPI cases are opened automatically.
An averagely inept seller may know nothing about dealing with GSP items and not know that they have automatic INR set.
So it's probably not direct action by the seller, it's just the super complicated modern ebay.
If you can find a 'request invoice' button on each of the items in your buying history, and use all three, this will detach the items from the GSP. THis may not help as the seller may well remain totally mystified.