Insider Threat is real, can't discount that at all. What I can tell you as someone who participates in OSINT competitions and has engaged in red team activities, Linkedin is always the first stop when shopping for info.

Edit: Also wanted to mention 3 out of 4 incidents I am involved in is related to insider threat.

We can't discount the insider threat at all, but it's very easy to discount such shallow measures. Also, this wasn't a competition, and even there "the first stop" tells us nothing about its effectiveness (maybe the next 5 steps take 5 mins longer, but are even more accurate, so the benefit of the ban would still not exist)