You are very correct. It's a wise decision for a person that have a lump sum amount to accumulate Bitcoin as much as possible without delay because Bitcoin is very volatile and while delaying and still contemplating on DCA or waiting for the price to dip before buying the price may skyrocket beyond the person budget.
Surely I agree with you that if a person has money to lump sum once at go, he should invest it fast as possible without hesitation but that does not mean that Bitcoin will outgrown the impossibility of buying according to your Budget. Of course that is a misinformation, Bitcoin nature permit any one to buy according to their budget. For example if 1 Bitcoin today is $100k and you have $100k to buy 1 Bitcoin but due to procrastinatination you somehow waited for Bitcoin to increase to $120k surely you will not be able to buy 1 Bitcoin $100k, you will be able to afford 0.833
BTC with $100k and not 1 or 0.99
BTC. So surely Bitcoin is affordable with any amount you have but not less than $5.
Yes, Bitcoin volatility rate is high with no exception to how the price might increase, still we should have in mind that same way the price have the possibility of increasing while holding funds to lump sum, the price of Bitcoin might also decide to fall below giving the investor an opportunity to invest and hold more portions of Bitcoin using that same amount. Delays with funds can positively or negative affect the impact of our portfolio, purchasing at a high price or even lower.
1 Bitcoin = $100K (At when due)
0.83 Bitcoin = $100K (When the price of Bitcoin increase)
1.2 Bitcoin = $100K (By time the price of Bitcoin reduces)
For those who do not want to make use of the DCA approach and love to implement the lump sum method should consider proper timing, not procrastination or delay understanding the market and knowing when to buy with the consciousness of holding for a long term.