If your friend sells altcoins that have no price development at all, that is the right choice, asked to be exchanged again for bitcoin. Of course this will be profitable for investment. Because of seeing conditions in the market, bitcoin has experienced many price changes. and I think there's no need to worry if your friend has exchanged altcoins and invested in bitcoin.
Diversification will be the best choice for those dead coins, it is no sense if we keep holding with them better to sell it even we only get a small amount.
This is what I did before and it actually works, and besides, it helps to increase my funds.
It could be best if he sells it earlier and invests in Bitcoin before bull run cause he actually is profiting by now.