The EGR system is a monitored system, and a Emission system so you would absolutely get a CEL and code if there was a problem there.
If the vacuum pulse stopped with EGR capped then my guess would be that it is "normal" or at least not outside of computers range for proper operation.
EGR system has 3 parts, 4 if you include the computer(PCM)
EGR Valve
EGR Modulator/solenoid
and
DPFE sensor, part you described
Computer monitors engine load, under load the cylinder temps go up, which will cause higher NOX emissions, toxic gas.
So computer will pulse 12volts to EGR Solenoid, this causes vacuum to be applied to the EGR Valve, and this lets some exhaust gas flow into the intake.
The HOT exhaust gases mixed with the air/fuel mix cause the mix to burn slower in the cylinders, so they burn cooler, and less NOX.
DPFE sensor is the feedback to the computer on how far open the EGR Valve is, how much exhaust gas is flowing into the intake.
One hose on the DPFE sensor is closer to the EGR valve than the other so the closer hose will have a lower pressure as EGR Valve opens.
This pressure difference tells the computer how much exhaust is flowing into the intake.
DPFE = differential pressure feedback
The computer might be programmed to stop pulsing EGR solenoid to test if DPFE sensor is working, when EGR solenoid closes vacuum in intake goes up and DPFE should be 0 because EGR Valve is closed.
Then after 3 or 4 seconds computer activates EGR solenoid again, vacuum goes down, adding exhaust gases back to intake to stop the NOX production
It kind of makes sense since there really is no other way to test/monitor the system except when it is being used
One heads up on DPFE sensors, now that you know where it is, exhaust has water vapor in it, a by product of burning Hydro carbons(H) with air(Oxygen) is H2O(water), which is why exhaust systems rust from the inside out,
The hoses on the DPFE sensor get water vapor inside, and so do DPFE chambers
This can cause bad pressure readings but it also causes DPFE sensor to get corroded inside.
Not a bad idea to make sure hoses are clear once a year, do not reverse them, lol.