Emergency fund is needed only after starting investment, that is why emergency fund is needed where you can continue investing Bitcoin regularly on a weekly basis. Investing Bitcoin according to the DCA method will allow you to buy Bitcoin regularly and you will also be able to hold it for a long time.
If you spend time in illness, then you may refrain from investing because you may not have money saved, then you can invest Bitcoin from emergency fund. Regular DCA method will be followed to deal with danger and to sustain Bitcoin investment for a long time.
Your advice is good, but when someone invests in DCA method, he has to take a long term plan like he will continue the investment for the next 10 years and then he will think about the profit (this is my personal opinion).
Now if someone thinks that he will manage the investment for only 1 year and then he will make a good profit from it, then good results may not come. So in this case, long term planning is important.