I’m can tell you that PIRs seem to be sensitive to just about everything… bright lights, reflections, etc. By design, it senses a heat signature, and that’s what gets translated into motion detection. So, what it “sees” is the temperature that is different than what is around that object. A hot car engine on a cold day may get picked up faster than a human on a very warm day. Maybe. Blink most certainly uses a less-precise PIR in return for lower design costs,
Contributors much smarter than I will certainly weigh in on this.