Author here: the code increases are small indeed. Most blocks only have one version, so the size increases are negligible in most cases, sometimes there is no i

Author here: the code increases are small indeed. Most blocks only have one version, so the size increases are negligible in most cases, sometimes there is no increase at all. We also have a simple mechanism to completely prevent pathological explosions, which is to say that any given block can't have more than some number K versions.