If you are really into altcoin investing then this is a wise move definitely. Alts behavior is harder to predict than btc IMO so choosing only one alt will give you of higher chance of losing. You know, if the whales of that alt finally dump once and for all then it's game over. Diversifying your assets bring you greater chances of winning. But take note, be careful on picking the right one because sh*tcoins scattered around.

But if I will be asked, I still stick to btc as much as possible .