It is not a mistake.
Your items are listed with Simple Delivery so the buyer pays the postage cost to Ebay and Ebay issue a label or a QR code.
You don't have to ask for a paid label, using the new system it is created automatically. The tracking is added and the item is marked as sent, using the tracking from the prepaid label so payment to you will be delayed.
Read all about Simple Delivery using the link below.
https://www.ebay.co.uk/help/selling/posting-items/setting-postage-options/simple-delivery?id=5575&st...
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)