As a general comment, I have found the Core to be very specific in its arduino code requirements. That is, code that runs perfectly fine on an arduino will require some slight modification to properly run on the Core. As an example. I had an arduino sketch which used an IR proximity sensor to pulse LEDs below a specified threshold. On the arduino side, I hadn’t designated the digital pins to which the LEDs were connected as OUTPUT, yet the application ran perfectly fine. When I moved the code to the Core, the WebIDE required the digital pins to be set as OUTPUT, otherwise the app wouldn’t compile.
If anything, I suppose that’s a good thing as it taught me to be more explicit in my coding practices, but yes, I have noticed a slight difference between arduino and the Core.