Just for context, the M1's latency is fairly close to other LPDDR4(x) systems (Tigerlake and Zen3 SoCs). This is fairly typical of LPDDR4 compared to normal DDR4, part of the compromise.

Not the most scientific, but userbenchmark is useful because it has latency graphs available for millions of systems.

Latest gen Intel with LPDDR4x chips is well over 100ns https://www.userbenchmark.com/UserRun/40531587 While the same CPU is almost 40ns faster with SODIMMS of DDR4. https://www.userbenchmark.com/UserRun/40527352