Based on what you said, WiW, there is a 51% attack everytime a block is orphaned
so dozens of time per month! lol
The difference being that a block is usually orphaned because it came second to the miner (propagated the network slower) but wasn't shorter in terms of proof of work.
In this case they rejected a valid, longer proof of work chain in favor of making a shorter chain outpace the longer one with a majority of hashing power.
