How does a RPC work?

--Snip

 

Conceptualy you are right, in unity RPCs are always reliable anad ordered so you are guaranteed to receive updates currectly. Because you are not buffering it the future players will not receive it. Your character will be instantiate d in the however if you use Network.Instantiate since in unity's networking (built in one) you can not filter buffered RPCs at execution time.
You can even write this method as a setter for a property and sned the rpc there so whenever someone sets the health property it will be called but it's hiding what actually is being done probably .

Hope this helps (I said conceptually since i'm too tired of being capable of checking for small bugs)