A lot of sellers entire business is selling items that qualify for letter / flat postage, untracked. Why should eBay restrict sellers from using that service? I've shipped countless untracked letters and flats over the years. While I know I'd have to refund if a non-receipt claim is filed, so far I've had honest buyers in those categories. Most buyers are honest.
eBay just recently added letter / flats to the list of services - decades overdue. This is not an error and they should not be removing it.
It's up to the seller to know whether or not their item meets a carrier's physical requirements before selecting any service from the list. Sellers need to police themselves to make sure they're following the carrier's rules because if they're caught breaking the rules, it falls to the seller, not to eBay, to deal with the carrier's consequences.
Fortunately you figured it out before shipping and your loss of less than two bucks is basically nothing. Could have been more significant than that. The only item in your list of active and sold listings that might qualify for the service is item 186186430059.
