It's very hard to notice and very easy to attribute something else. The main symptom is your laptop heating up which is usually attributed to (1) You just have a slow MacBook, you should get a new one (2) During beta, "it's a beta and it's expected to heat up and be slow" (3) People not caring about temps because they use the laptop in clamshell mode

I believe this falls into the perfect definition of "slipped thru the cracks"