yea probably, Im not an uboot expert but for my board (from toradex), their recipes have a patch to the boot script (meta-mender-community/0001-Adapt-boot.cmd.in-to-Mender.patch at dunfell · mendersoftware/meta-mender-community · GitHub). This gets compiled down to a boot.scr file in my boot directory which reflects these changes.
Several other bsp layers does this too (for e.g meta-mender-community/boot.cmd.in at dunfell · mendersoftware/meta-mender-community · GitHub and meta-mender/boot.cmd.in at master · mendersoftware/meta-mender · GitHub)
I would imagine you would need to implement something similar as well (or atleast check that the mender_* commands are being called during boot