There is nothing wrong with that, he is simply stating up example so he can indeed put up any number into it but he forgot the vital point that a skilled trader wont even wait for a 10 % increase to sell it, it will be around 0.5-1 % to execute the sell for them
unless you can systematically, be good with selling at such low % in the long run, fees would be a problem, those are anyway good shorters traders,
a more bullish will wait a bit more before selling to squeeze the maximum amount possible, and the risk will rise too, of course
Fees are mostly 0.25 % which make up 0.5 % for both buy and sell which makes my argument stands on atleast 0.5 % because some exchanger apply a limit/instant execute which the fees only apply to the limit option and most chinese exchanger are applying 0 % fees anyway so it is a bless for trader
The bolded part is actually a standard way in trading. Practice do make things perfect which in this case a skilled trader will now on not how to limit order
i.e since the price is holding at $220 (for example )
Instead of buying a chunk of it for $219, trader mostly set up limit for the order and spread it well, in this case it will be buying at $219 , $218.8 , $218.6 and so on. By making it this way, it is easier to gain profit this way, the price of your buy order will be on the average of those all buy order. By doing this way then if the price is dropped to $218.8, then you will still have some tiny profit out of it because you are not buying them entirely at $219 but instead you spread it further to minimize the risk of losing it