I totally agree with you on this, Emergency funds are meant not to be touched but rather they are meant to foot the bills of unforseen circumstances. But for discretionary income one can decide on what to use it for, either for savings or what a view.but then most investors don't understand this principles and get it twisted so your point clearly state one save what remains out of paying their responsibility bills.
Emergency funds should be used in unexpected times so don't use them for anything other than emergencies, at least that's our principle on how to handle emergency funds.
Discretionary income is up to the individual what they do, so it is better to invest in bitcoi so that it can grow even more or divide discretionary funds with investments + your wishes are up to them, but I myself am more into investing because it is better for the long term.