I agree with you, but I think you're definitely talking more about teaching using a small microcontroller (Which a STM32 definitely qualifies as) rather then wh

I agree with you, but I think you're definitely talking more about teaching using a small microcontroller (Which a STM32 definitely qualifies as) rather then what they're doing here. The Raspberry Pi runs full Linux, so their code is a fair bit removed from direct hardware access and has a decent amount of boilerplate before you can begin to start messing around with GPIO. They do still eventually memory map the GPIOs, but IMO it's not really the same. That said, I think the AVR ATTiny and ATMega chips easily fit the bill, and possibly better. From a teaching perspective, they meet all of what you're talking about, and IMO they're better for simple circuits like flipping LEDs because they can really work with basically no extra components - you can just plug it into a breadboard like any other simple chip.