The test server is for what ever you want, not just testing new functionality, before a new patch.
You wanna try a 4 billion t3c in pvp, before taking it to nullsec? Test server. You wanna test the structures and fitting before spending isk? Test server. Are you confused about some mechanic in the game? Test server.
Its basically a persistent server for anything eve related, be it testing new fleet doctrines, new fits, stuctures or what ever, as you can “teleport around” and get all your ships imported from Tranquility, with simple commands.
Next time, go on the test server and anchor one of theese structures, like most other people do to test it, before handing out the isk on the real server.
I will agree, that the simulation should show you the right multiplier, did you report this “bug” to ccp, by any chance? It sounds like a bug or an oversight tbh.