Yes best binned chips of DDR4 4200 bellow JDEC SPEC 4200 DDR5. Indeed a stick with a set of the best binned chips for DDR4 will beat bellow average DDR5. But if we go that path, if we could had DDR at 4200, it would beat DDR4 by huge margin. That is just not possible.
But this is the end of the road for DDR4, there might be few higher performance kit in the near future, but that won't last and that will just extend slightly the limit of those memory. DDR5 are pretty untapped.
My understanding is to get good high speed memory stick, we need to have a very robust server/laptop/OEM desktop memory market that all use JDEC speed memory kit. They allow for mass production of chips that can be binned higher. Right now, not much use DDR5 except Alder Lake.
Once the Zen 4 Epic get launched and Sapphire rapid, we should see way more high speed kit. DDR5-8400 might become quickly the new DDR4-3200
and DDR5-8400 will completely destroy a DDR4-4200 kit.