When you seriously come to think about it - storing your Crypto in exchanges is better than using cold wallets.
The first main reason is that exchanges pay you an interest rate on your Crypto whilst cold wallets pay none.
The last time I checked, only few exchange site offer this kind interest, mostly exchange site that offer lending service are those that pay interest to their user according to the they have have coin.
It sad I wasted some minutes of my time surfing the link you provided in other read the remaining opinion you have but I dont see anything that seem to be information about the reason why saving crypto on exchange site is better than cold storage.