Yes, each architecture has its own way of dealing with "unruly" OEM boot args potentially patched in as well as compiled into the architecture's kernel. Some accept them, some ignore them completely, others munge them in subtle ways, such as when they are needed to select version in dual-firmware devices.
You'd have to look through the kernel patches to determine just how it is being done for your architecture.
target/linux/ramips/patches-4.14/0007-MIPS-ralink-copy-the-commandline-from-the-devicetree.patch might be interesting to examine...
For someone finding this in the future, the patch above is (April, 2019):
@@ -82,6 +82,8 @@ void __init plat_mem_setup(void)
+ strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE);