Happens every day, not a new scam, applies to much more than GPU's (although they were the popular target a few years ago).
These scams which are in the the 10's of billions per year are rampant EVERYWHERE, it is not an eBay thing.
I am not dissing your warning in any way, people need to be on guard at all times no matter where they sell.
One recent move by eBay (not sure if it applies to Canada), Sellers if they print shipping labels via eBay can no longer change the Zip Code, you can still make some edits to the address (eg: add an Apt No.) but the zip code is locked.
eBay made no announcement but it's clear this change was to prevent at least some of the scam attempts that you encountered.

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915
- answering Trolls is voluntary, my policy is not to participate.