The included 4.5″ guard is actually the N309159, which is called the “4.5in / JUMBO FLAP” guard. I subsequently purchased the N306360 4.5″ guard, which is perfect for using with standard non-hubbed flap-discs or grinding discs. Further, the correct 4.5″ Type 1 cutting guard for this grinder is N311419.
https://www.amazon.com/DEWALT-DWE402-2-Inch-11-Amp-Grinder/dp/B00RVZ7DNO