Re: Hypothetically if your daycare provider.....
As a parent, I would be very happy that a provider first raised concerns with me ("you know, I noticed that...."). However, anything beyond that would start to raise my hackles, esp if provider gave LO a test or sent her home with one. I know it's not MEANT to be, but it would rub me the wrong way, like "I am better at this than you." Now, I KNOW that my daycare providers are at least more experienced than me (FTM) but I would still get sensitive (perhaps unnecessarily, but when are we ever 100% objective when it comes to our kids)?
What I would react well to - "Hey, we did XYZ today with LO and she really loved it/figured it out fast/learned something." Just present it more as "here's something they enjoyed doing today" rather than "here's what I would do if I were you."