This is the first intelligent issue raised by someone in this forum. I commend you for actually sitting down and attempting to find a flaw in the system, and not shouting and crying about "nfts" when the post is about rare sats.

I believe that putting the fee last is the first arguably arbitrary convention. I wouldn't necessarily make the economic argument. Maybe it makes more sense to have the first sats flow into the fee because the coinbase transaction that pays the miner is the first one in the "to-be-confirmed" block. One could also argue that the fee is simply the remainder of the amount in the inputs minus the amount in the outputs (which it is) and that's why you pay the fee last because you need to have a set amount for the outputs to calculate the fees. There are arguments for both arrangements, that's why I agree with you that this may be indeed the single arbitrary consensus about rare sats.