Since installing 10.13, I've noticed that the fan on my MBP starts shortly after the screensaver activates. This is very unusual, considering my fan almost never came on under 10.12. I thought it may have just been a fan issue, so I did an SMC reset. That didn't fix it. So, today, I started testing it to see what the deal is. I'd invoke the screensaver and then check the temp and CPU usage. The results were pretty consistent each time. When I'd activate the screensaver, the temp would steadily rise to 100 °C, kicking the fan on. Oddly enough, though, the CPU usage stayed below 5%. What is going on here?