Come to think of it I really only need two sets .

   Come to think of it I really only need two sets . Still curious about how they function 

   My locks are closed on the Jimmy Skiff II.  When not in use I remove the oar with lock installed and place both on the floor or the seat.  Not sure what you are thinking. 

Sliding the oars off and out of the closed lock............is too much work. 

I used one set of closed and one set of open locks for the purpose you describe on my NE Dory. It works reasonably well. Ultimately, storing oars in a dinghy will always be a challenge. With the open locks, there is a danger they fall out so you must add a line or thick non corroding metal loop to the hole at the bottom of the part inserted into the oarlock receiver (circular hole). With the riser, you have little space but it works. I used a piece of 12 gage copper electrical wire formed into a rough ring to stop the open lock from getting out of the hole. It is hard to explain in words. Any solution that stopes the oarlock from coming out when not wanted is good enough. Also, if you going some distance in the dinghy and it is bouncing, you will likely want to tie or bungie down the oar in the open lock to stop it jumping out.

On my boat, it isn't feasible to place the oars on the floor. It might work in some boats - especially if the oars are short relative to the boat length. 

   I have closed locks for my oars and they work well.

I am actually thinking of adding a third location on my skerry for storing the oars while under sail. Haven't executed yet but the plan is to have a cradle either far forward or far aft (with the latter I would want it to help with back support) I also have inwales, so I might set up a system that can utilize those and then be removed.

 On my dory  I use one set of closed oar locks along with one set of open oar locks for just the purpose you mention.  I row from the center station using the closed oar locks. When sailing, I rotate the blades toward the bow and rest them in the open oar locks.