fucking hell, i couldn't replace the transaction by any higher fee i got the error saying insufficient fees. wtf
Weird. All I got was "Error: txn-mempool-conflict" when trying to push the new TX (key was cracked in seconds).
So I guess it depends on how to push a raw TX bypassing this error. I'm sure a P2P node can bypass this problem. So not sure what exactly was proven here, except some mempool rules depending on who you broadcast the TX to.