Queuing as 4 roles

So recently this thread became popular: http://boards.na.leagueoflegends.com/en/c/gameplay-balance/EGtgQq31-please-riot-i-need-to-negate-a-role and I noticed a two sided argument forming. People seem to be confused on the whole supply and demand* involved with having a fill except X option. Queuing as 4 roles would decrease queue times a player because they can increase the supply to satisfy the demand of 4 roles instead of just 2.

Imagine a player queues up for top/mid but junglers are in high demand. Now this player can play top/mid/jungle equally well but because he can't know that junglers are in high demand (RIP teambuilder), he now has to wait 10 minutes in queue to get into a game. He could have been in a game in say 5 minutes if he could have queued for all 3 roles.

*Supply refers to the amount of a product available for use. Demand refers to the amount of product desired by consumers.