It makes sense: Lee Bergere had to deliver his line "If those are weapons, please lower them" line. The scene needed to blocked so that the guards' phasers were drawn and leveled at Lincoln.
True enough, that reinforces that it was intended from the beginning. Clearly they were ready for diplomatic functions such as greeting dignitaries (i.e. Journey to Babel
), and they didn't point their weapons at Sarek, so it must've been Lincoln-specific such as you say. It just looked odd to me, because otherwise they were respectful to Lincoln in every way. I wasn't implying they were in error, but I guess it was a good thing that that 'young and inexperienced' guard from Friday's Child