The separate light-only sticks are useful if you want the appearance of all four slots filled: having four RAM sticks usually forces a slower memory speed (as the target market typically overclocks their RAM*), so unless you actually need a lot of RAM and can’t get a 2x32 or 2x48 etc kit you’re better off with the fakes.

Edit: this is also why some “extreme overclocking”-type motherboards** only have two DIMM slots: having four actively opposes their purpose.

* And yes, loading an XMP/EXPO profile to get the advertised 3000CL60 or w/e counts!

** i.e. https://rog.asus.com/us/motherboards/rog-crosshair/rog-cross...

All 4 of my PC's are 128GB (2 sticks each, no filler) and my home server is 512GB