this just means the M1 has a fixed function block for your codec or whatever else you're doing and the 3090 doesn't. or that your video software is crazy broken.
it obviously doesn't matter for your workload, ultimately the M1 is faster and that's all that matters for you. just highlighting that this isn't magic, just hardware matched to use case.
It also means that your hardware has a tendency to "strangely become supper slow" when video codecs change over time.
But then they don't change that often.
Your probably change your apple laptop more often.
And given that codecs are pretty much the only "high performance" use-case apples target audience has to a high degree putting special hardware in to make it go fast is the right way to go.
it obviously doesn't matter for your workload, ultimately the M1 is faster and that's all that matters for you. just highlighting that this isn't magic, just hardware matched to use case.