[2420] question about "isServer" in builder.js

Hy all, I was playing around with the babel configuration, and somehow I thought it's a good idea to target the server's webpack with latest node and the "non server"/frontend with ie: 9...

So I did something like this in nuxt.config.js:

 babel: {
        presets: function(isServer) {
            return [
                [
                'vue-app', {
                    targets: isServer ? { node: 'current' } : {ie: 9, uglify: true}
                }]
            ];
        }
    }

I got this by studying the builder.js file..there is a similar construct: targets: isServer ? { node: '8.0.0' } : { ie: 9, uglify: true }

So far so good, but now my application fails on internet explorer, safari and co.. (let is not allowed,..) looks like the transpile action targets the current node, and not ie 9 for frontend. Everythigng starts working again if i just target ie: 9, indepent of "isServer" flag.

What do I miss here? Is it somehow related to SSR that my iexplorer gets now the "wrong" javascript? Or is the purpose of this "isServer" flag something else and I just misused it?

Thanks Simon Ps.: using nuxt 1.0.0-gh-ae754af (nuxt@next latest)