I agree with you, because newbie investors has no business with diversification since they are just getting started with bitcoin. what should be the focus of newbie investors is the on going bitcoin accumulation, they should be more concerned about the on going bitcoin buying using the DCA method and hold for long term 4 to 10 years or more and not think about diversification.
Newbies are not ignorant of everything because the diversification you are saying could be something not even related to Bitcoin and you no that a newbie in Bitcoin might not be a newbie in the outside and they might even no better outside than a person who knows a lot about Bitcoin investment, so actually there is no discrimination about it. It can be said about what you think when the newbie is saying to leave Bitcoin and choose other crypto, however most people that does more of this diversification are people who says they have accumulated alot already.