Not exactly normal. I have had a fair share of control valve mounting gaskets to "blow out" at the main pressure oil gallery feeding into the control valve assembly. When the gasket blows out, it often loses a section of gasket and the breach simply sprays oil back into the transmission case/sump, so you never know it has happened until the truck begins to act up.
And your description about the 5 second delay is not exactly how failure of that gasket usually causes the truck to behave.
Failure of the gasket as I described usually causes the transmission to have a hesitation before beginning to move when the accelerator pedal is pressed down. The hesitation occurs every time the truck stops and is asked to move again, until the gasket is replaced.
I wonder if the 5 second delay you are seeing might also be an indicator of an early stage of the gasket blowing out in that it could be allowing the gallery above the pump to "siphon" or drain itself empty when the truck remains parked for a long period.
I will PM you a photo of a failed gasket on one of these trucks.
Our fix to prevent future blowouts has been to use an automatic center punch and put a circle of punch marks about 3/16" apart around the mail oil gallery on the aluminum control valve body. The pin punch marks are just enough upset to grip the gasket and keep it from blowing out due to the "balloon effect".