Raspberry Pi 4: apply-overlays-dtmerge.nix always skips overlays

[Gigahawk]

When building off master, it seems like none of the overlays I've selected are getting applied:

config:

  hardware.raspberry-pi."4".apply-overlays-dtmerge.enable = true;

  hardware.deviceTree = {
    enable = true;
    filter = "bcm2711-rpi-cm4.dtb";
    overlays = [
      rec {
        name = "dwc2";
        dtboFile = "${config.boot.kernelPackages.kernel}/dtbs/overlays/${name}.dtbo";
      }
      rec {
        name = "tc358743";
        dtboFile = "${config.boot.kernelPackages.kernel}/dtbs/overlays/${name}.dtbo";
      }
      rec {
        name = "i2c1";
        dtboFile = "${config.boot.kernelPackages.kernel}/dtbs/overlays/${name}.dtbo";
      }
    ];
  };

When building I get:

$ nix log /nix/store/rqzzj81h8dmal41yvnvkj2qpyalskdwq-device-tree-overlays
./broadcom -> /nix/store/rqzzj81h8dmal41yvnvkj2qpyalskdwq-device-tree-overlays/./broadcom
'./broadcom/bcm2711-rpi-cm4.dtb' -> '/nix/store/rqzzj81h8dmal41yvnvkj2qpyalskdwq-device-tree-overlays/./broadcom/bcm2711-rpi-cm4.dtb'
Skipping overlay rpi4-cpu-revision: incompatible with bcm2711-rpi-cm4.dtb
Skipping overlay dwc2: incompatible with bcm2711-rpi-cm4.dtb
Skipping overlay tc358743: incompatible with bcm2711-rpi-cm4.dtb
Skipping overlay i2c1: incompatible with bcm2711-rpi-cm4.dtb

However, I've made a branch where the compatibility check is removed and everything seems to work fine.
It seems like the overlays use slightly different compatible strings from the base tree, but are otherwise compatible.

Just wanted to understand what the point of this check was, my understanding was that at runtime incompatible nodes in the device tree just get ignored so it should be fine to always add them.