What you actually just said: “Hey, why don’t you spend
some time going through your schedule, pick out some times
that work and email them to me. I’ll then sit back and
pick one that I like.”
1) When you suggest a bunch of possibilities yourself, they will still have to go through their schedule to see if they are free at any of those particular moments.2) Going through your schedule hunting for specific moments takes longer than just finding the first empty spot that they might want to fill with your particular request.
3) Since they are in demand and their schedules are full, it is quite unlikely that any of your chosen times will fit them. As a result, they will still have to do the same work to make a 'counteroffer'.
Any arguments in favor of the thesis are lacking. It's just someone venting an opinion.