I don't think there will ever be great clarity. It depends so much on the broker. The one I used before TOS would have you "buy" or "sell" to close ....or "buy" or "sell" to open. One reason TOS just has sell or buy is that they don't see a multitude of potential positions as specific positions. Say you have a book of puts and calls on the SPX....depending on how you arrange them you could have any number of transactions from IC's to B-flys' to verticals, calendars, or diagonals. Therefore for simplicity perhaps it is just easier to say when you are short (ie you have received premium) then you have a sell and when you are long (you paid a premium) you have a buy.