This. I would rather post on any other social media site at work than Linkedin. It's a major signal that the person is looking for work.
1. That’s the default presumption (rather than someone doing networking for their current role)
2. Where “looking for another job” is a point of contention
Any good senior engineer should be keeping in touch with others in the industry. And good teams are made up of people with good communication skills who want to be there.