It all works. DDR4 is DDR4. MSI like All the other vendors is very lax about older stuff being updated. So you'll see B450 mobo's that only have ram go upto 3200MHz, because that was the fastest ram available back then. But once you exceed the memory controller speed and get into (OC) that's xmp, and it's all fair game. A B450 mobo that has a listed 3200MHz (OC) will run DDR4-3600 or DDR4-4400MHz with a 5000 series Ryzen. It won't do it with a 1000 series Ryzen, that's a cpu limitation, not a motherboard limitation.
But if you look at that picture, which was direct from that compatibility that was posted, DDR3-1600 is most definitely Not compatible by any means, it's physically different ram. Doesn't even physically fit in the DDR4 slots.
There's only a dozen or so actual ram vendors. Ppl like Samsung, SkHynix, Nanya, Micron etc. They make all the ram for everyone and put a different heatsink and paint job on the outside. But the guts are the same. Corsair LPX uses the same SkHynix as Team Group, g-skill uses the same Samsung B-die in their Trident-Z as Patriot Elite etc. Take the heatsink off a LPX and a Team Vulcan, and it's impossible to tell them apart physically, because they are the same pcb, same memory chips, same layout, same ram.
Model numbers are worse. Just in gskill Trident-Z DDR4 there's over 3000 different model numbers. The camo version is identical to the white/gray or black/white, but because of a different color, they get a different model number. Msi might test the white at 3200, 2stick kit, 8Gb, but that's realistically identical to the black/white, 4-stick, 8Gb 3200. Same ram, same stats, 2 extra sticks of the same thing, totally different model number.
It's like seeing a picture of a black 2022 Dodge Charger R/T with the stats saying it'll do 0-60mph in 5.0 seconds and average 22mpg. That doesn't just apply to the Black cars, that applies to the Pink, Purple, Red, Green, White and Blue Dodge Charger R/T as well. Same car, different color.
The XMP (OC) rating on ram simply states that the factory has tested and certified that the ram Will attain and be stable at that speed. It does not guarantee, in writing or implication, that it will do so on every motherboard, or any motherboard you might own.