[seba_dos1]

I'd guess that power consumption characteristics of those two i.MX8 variants are different enough to explain that choice.

[floatboth]

Well, the mainstream phones have much more powerful processors than Cortex-A53, they just power manage them well…

[seba_dos1]

I wouldn't expect a SoC that's not even targeted for mobiles to "power manage them well". Mainstream phones are completely irrelevant there.