Empress Defeated (in kMST)

I don't understand the relevance of whether it's a dirct copy or not, if everything matches, everything matches.

All a p.server has to do to play with a certain version is to give packets to the player that the client version recognizes.

For those boss notices it's just sending "line of blue text, contents 'To the team that finally defeated Horned Tail after countless attempts, etc.'" to everyone logged on. It's not some "someone has defeated HT" event that the client has to interpret - just a line of chat. Most of them are set up to match GMS in some ways and diverge in others - for example, OdinMS had true instancing of most PQs, because it handled the maps differently server side - all the client has to understand is "you are in map number x, with players y, z, standing in certain spots using their skills" and it's happy.

They're also not vulnerable to the same dupe exploits because the item DB is set up more sensibly.