St Louis 20% Rule??

[Lamar Cannon]

I just got off the phone with an escrow officer in St. Louis and I was told that they can only do assignments or double closes on wholesale deals if the spread is 20% of purchase price or less. Is this a common rule or do you all think it is specific to that title company and their underwriters? 

We are getting these houses so cheap that a 5k assignment is 100% or more of purchase price.