This is what i hand in mind whit "manually handing of futures". In this case you have to write

   Promise1 = f1(); Promise2 = f2();
   v1,v2 = await Join(Promise1, Promise2);
   return v1 + v2

I think this is just too much of synthactic noise.

On the other hand, it is necessary becase some of underlying async calls can be order dependend.

for example

    await sock.rec(1) == 'A' && await sock.rec(1) == 'B'

checks that first received socket byte is A and second is B. This is clearly order dependant that can't be executed concurrently out of order.