I honestly feel the description of reserve funds can be given to non-discretionary funds or emergency funds if there are added context:
Context 1 : If the "extra expenses" was already budgeted before hand, then it should be non-discretionary funds.
Context 2: If the "extra expenses" is made after the income comes in, that is it wasn't planned for before hand, it should be under emergency funds.
Personally, I feel Reserved Funds are essentially savings set aside to achieve a particular goal ranging from just extra money saved for the purpose of saving to buying or achieving something huge like buying a car, house, planning a wedding etc.
Other than this, I agree with your assessment generally
Questioning that is much okay cause people get confused on it alot. Well thanks for the addition, the reserve fubds almost seem like both essential and emergency fund cause it can be planned or unplanned, planned in the sense that, for instance you could be paying a tuition fees in few months time or renewing a decoder/Netflix subscription.
Where it seems unplanned and looks like the emergency funds, is in cases like repairing a spoilt roof or fixing a spoilt door, you didn't plan for that to happen but know it might happen anytime, but it's different from emergency funds and discretionary income cause it's not basically used for investment or used to solve real time emergency situations that deals with survival, however I purposely think it should come after an income because it's non negotiable and people could spend it on investments if it comes after discretionary income which isn't a good act.
The difference is not quite much. I just put all of them in a single category.
The main point is to have a spare amount at hand in cases where needed. This helps you avoid going to your investment unconsciously. If we separate this into too many categories, one might get confused to some extent.
Though I see the need for your break down, which is very important and shows the usefulness of why we need to have a spare amount at hand while keeping our investment amount growing.
The difference might not be too much but it's clear, I had to break it down for beginners to understand and know the right funds to channel for investment so they don't go using their emergency funds or reserve funds for investment, most importantly emergency funds and end up complicating the investment on the long run.
The way I explained it is very understandable, except the person who find it confusing is kinda dull in comprehension and needs broad explanation to understand simple things like these. Ofcourse they're of separate categories cause they're not same thing, do you think they're?