You mentioned in your post from nearly two years ago (FreeRtos porting to Raspberry Pi 3) that you were wanting this for “newlings” to learn RTOS. And that Raspberry Pis are common in teaching environments. Trying to teach RTOS, and specifically FreeRTOS, for the reasons that @richard-damon so detailedly mentioned would be far more difficult on a Raspberry Pi. There would be many more minutiae details for newcomers to have to know.
What I’ve more commonly seen in higher education institutions around the world are students using lower powered hardware (e.g. from Microchip, ST Microelectronics, Espressif, and others) in their embedded development courses. These dev kits can be had by students be found for $2-10 from various retailers.
Lastly, you’re bringing the need for processing performance. We have some pretty powerful boards like the Xilinx option that @rtel mentioned. However, most new students will never need that level performance. Even the ESP8266 at 40MHz is underutilized in many cases until they need the memory for IoT and/or machine learning applications.