Deposit on a cash offer?

[Bob Romano]

I am about to make a cash offer for a SFH, my realtor insist that I still have to put at least 10% down ( he wants 20%) I said " why do i have to put anything down when we will be closing in 10 days on an all cash deal of $215k ? He insist you still have to put something down to show Im serious.

Is this normal?