To commit work you need to include a public key that is used as the collection address for coin-base / mining rewards.
Assuming that you would never use someone else's key (or that the whole network would never use  a single public key) every commitment of work will LOOK different even if they (miraculously) ended up on the same hash collision. Not to mention the ability to publish this block means that they get to commit their transactions from the mempool to that block, therefore each block will also vary in how it appears to other nodes.