Contracts and Agreements: Certified Letter from Employer Regarding Confidentiality Clause

I received a certified letter from one of my employers stating that I needed to remember my contractor agreement with them and be mindful of not sharing their IP or methodologies with one if their competitors with whom I also work. is this normal? I signed the contractor agreement and cleared their security and background checks.

They only know who I work with from LinkedIn, so I found it odd that the HR director had viewed my profile one day and the letter turned up two days later. I don’t care that they know, but find it discomfiting to receive a “reminder” in which they are “confident” I know my place! I have no non-compete, obviously. Is it paranoia?

Thoughts appreciated.

Contracts and Agreements: Certified Letter from Employer Regarding Confidentiality Clause