Aside from the “Hmm, am I sure that I can purchase a resistor in 402?” comment… Let’s say that I didn’t find it (I mean, when you think about it, maybe you realize at a later time that you needed a 0.01% tolerance, or maybe a 10W-rated resistor, so that perhaps you will not find it in 402).
So, how is that a problem? I mean: how is this a problem different than the one you have when a symbol does not have a footprint? When you finally decide which part you need, you have to change the footprint: you either change it from 402 to, say TO-220, or you change it from “empty” to TO-220. How was that different? (plus, this is an unlikely occurrence: if you chose a 402 up-front, it is probably because it wasn’t a 10W resistor or whatever resistor that you’ll only find in TO-220; so, it is most-likely that you will find it in the package that you specified initially).