It all depends on what you are protecting it from. If you are talking about "overload" then 310.15 rules and that is the case when you size to line to neutral loads. If you are just protecting it from a line to neutral fault that is short circuit protection and you can use 250.122.
When you think about it, we don't seem to have a problem sizing EGCs with 250.122 and that is sufficient to clear a ground fault.
I agree there was a problem when they only used 220.61 and you could end up with a very small neutral that might not clear a bolted L/N fault.
