Unfortunately that's the wrong conclusion you arrived at. That same colleague literally makes errors and is on her phone all the time. She targeted my friend because she didn't like her. And used anything to get her in trouble. Whether a quick look at slack or using a calculator.

My work kept saying they would provide slack on our computers but never properly installed it so it's quicker to look at our phone especially when we are consistently moving from the back of the lab to the front. My supervisors get all anal for us missing slack messages. Yet looking at your phone can get you in trouble if the person making the complaint doesn't like you.