Just because it’s in a Hollywood film does not make it correct.
Any Marine will tell you this is wrong
Do not use Taps to lower the U.S. Flag.
It is not authorized, it’s incorrect, and, most importantly, inappropriate to use Taps in this manner (echo or otherwise).
There is NO military manual that states the call to be used as a flag lowering. If there is, please let me know…
The correct calls for lowering the flag on United States military bases are To The Color or Retreat depending on what branch you are in.
Here is information on a Retreat Ceremony