I suspect it depends on what you consider "turning down a fight."
Joe Silva doesn't ask "is there a day that would work well for you to fight so-and-so?"
He simply asks "Do you want to fight JDS on May 25th?"
Frequently, the fighters respond with "well I want to fight (insert opponent's name here) but not on (insert date here)".
That's turning down the fight...at least according to DW. The fight isn't on whatever day you want...it's on May 25th.
Lots of fighters though have a more liberal opinion about what constitutes "turning down a fight".