"cash in hand" but I certainly did it no problem on a $5 table somewhere like Bellagio or Mirage in June.

That is, for example, AFTER the ball has spun, throwing $100 at the dealer and saying "11 and neighbours by $15, change on 8/11 split"
That is a "call bet". Usual practice on a $5 raceway table, where no-one calls their neighbours until the ball is spinning

It is different to "Money Plays", which would allow me to put $25 in notes on that 8/11 split. I agree that is rare. But, banknotes on red or black may still be taken. I dont know if Gene knows if there are any regs. I suspect it is house rules, and may be more for accountability, not wanting to slow the game down (if two people are playing money it wont be long before they have to re-run the video to see whose bet it was)