M1 memory latency is 100ns, which wasn't really competitive with amd/intel at the time (70 something nano). Any SSD read be an order of magnitude slower than reading from ram - something to the tune of 5gb/s version vs 70gb/s for the SOC ram. For comparison, the intel trashcan mac pro clocked in at 60gb/sec a decade prior.
Reference:
https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste...
https://www.anandtech.com/show/16214/amd-zen-3-ryzen-deep-di...