The fact that /var can do some math does not mean it can do everything that $calc() does. Just using //var %a = 1 + 2 + 3 will fail as well.
I never said that nor I want the feature to be extended (pointless as you said, just use $calc) but :
That is simply a limitation of /var and isn't a bug
The fact that variable's mathematical abilities doesn't return the same result as $calc for the same expression is a limitation of /var and so it's not a bug ? What are you talking about.. ?
It is expected that both methods return the same results.
If $calc was throwing an error when dividing by 0, wouldn't you expect the same thing happening when dividing by 0 with variables ?
When something unexpected happens, it's a bug for me.