Every strategies has it's prons and cons and there are several reasons for investors choice of strategies and there is no reason for this arguments or making any forms or comparisons. However, it seems that you are misunderstanding the Idea and concepts of the lump summing such that the fact that any investor will option to make the use of the lump summing as a strategy does not necessarily means that there was no provisions made for emergency funds or to have not taken care of his other needs and probably might not even be as a result of fomo. The Idea of lump summing has more to do with investing right away with a huge sum of money readily made available for investment after ensuring your other needs are taken care of including emergency funds which is Very important as individual even without venturing in to investment.
. Just as you have rightly stated, every investors should adopt a strategy that suits him/her, but it should be combined with DCA. The way the market tends to be these days relying on one strategy might not really go well. For me if I have a big sum of money to invest, I will divide it into two, use half for lump sum and use the second part to be doing DCA every week. This way you will benefit from different market conditions.
lump sum can be used by any investor both rich and average that wishes to put in some money into bitcoin irrespective of the price or timing in the market, i like to see my lump sum investment like hey i just received an extra cash and I think I need to buy some bitcoin with it so instead of just using it for DCA or adding it to my DCA amount, I rather just put it at once into bitcoin, yeah we can get confused especially if the amount is not big enough if we actually made a lump sum investment, but if its more than the Normal DCA investment then we can call it a lump sum investment.