IMHO surprisingly low. Still not clear to me why they don't just port these things to ARM or similar?

I don't know either what they meant, but for comparison NumWorks calculators are clocked at 216 MHz (100 MHz for the older models, and 550 MHz for some of the latest ones, but not everywhere), so it doesn't look that much out of the ordinary, maybe a little underpowered from my experience with the first NumWorks but eh idk it's a calculator and unlike the first NumWorks they don't try to do CAS.

Faster than a base-config SGI O2, with a MIPS R10000 at 150 MHz! /s