I'm no expert and can't examine all the bits in detail, however, I trust the likes of FSF and Stallman. So far, they haven't given approval to any laptop built after mid 2000s. I wonder why.
Points for creativity, but in my opinion this borders on rule-lawyering with not much benefit. The code that tells the ARM/M4 to load stuff from that SPI flash can be easily changed, it's in the bootloader, so it can change that code before putting it into the DDRC.
Also I’m not sure what the stance of RYF is regarding controller (non-CPU) firmware, as iMX8M needs a blob _in_ the DDR4 controller PHY.