A good test whether a question is a arduino user-level question is whether you can replace all mention of "arduino" with "microcontroller" or "microcontroller development board".
If the question still makes sense, then it's not about the arduinoness. Of course then the OP should have done the substitution in the first place to not give the impression of a arduino-specific question. When "arduino" is mentioned, particularly in the title, then you can't really blame people for closing or migrating without looking at it more closely.
On the other hand, if the question makes no sense without specifically mentioning "arduino", then it's about the arduinoness and doesn't belong here.
The question you linked to fits into the second category. Especially considering code was shown, it doesn't make sense outside the arduino context. It was correctly migrated.