Your point is valid, maximizing Bitcoin allocation early can accelerate long term gains, but it is also a higher risk approach. The challenge is that without a decent emergency fund, unexpected expenses could force you to sell Bitcoin at an unfavourable price, effectively turning a temporary dip into a real loss.
It's impossible for you to have a decent emergency funds in the beginning of your bitcoin accumulation phase because you need up to a year or two to be able to build up an emergency funds of three months of your income. This is the main reason why it's important to build your emergency funds with the same amount that you are using to DCA for a start til you have built up your emergency funds.
Emergency may come or not, therefore allocating more money to your emergency funds and allow your bitcoin investmet to be two times smaller than your bitcoin investment is wrong because of debasement of fiat currency overtime.
Of course, it is important to know when one has an emergency before saving Bitcoin. This should be at least 6-7 months of his necessary expenses in the emergency fund. Yes, you are right, he can save some amount of Bitcoin every month until he accumulates his emergency fund. Which he will gradually accumulate his emergency fund and start saving Bitcoin with it.
There is no guarantee that an emergency will not come, when he invests some amount of money in Bitcoin, if at that time he needs money in an emergency, he can spend the money in his emergency fund, which will not put any pressure on his Bitcoin investment.