Looking at its specs, the RPi 500 will be suitable for a MoodleBox just like the RPi 400, with more power and memory.
I don't think the advantage this model is the case, since buying (or printing) one for a RPi 4B or RPi 5 is quite easy and affordable. But for someone who needs a small Linux box for everyday computing plus a MoodleBox, this model is IMHO very much interesting.
Disclaimer: I've not tried this new model, either as a simple desktop Linux computer or as a MoodleBox, so bear with me.