Understanding this, if someone wants to invest their emergency fund with risk, then I said that they should invest some part of it instead of investing the whole amount.
However, I think it is better to keep the emergency fund in fiat.
This is terribly wrong, your emergency funds is not meant for investing, even though you are investing only a cent of it, no, don't do that.
This is why reverse funds is set aside, so that a dip buying opportunity can be utilized proper, but thinking to invest part of your emergency funds is a terrible financial mistake that you might pay dearly for if any serious real life emergency situation arise during that period of time you invest some part of it.
Your emergency funds should only be tempered with when a serious real life emergency situation that threatens your Bitcoin holdings, nothing else.