As I understand it, 'Guard post' is supposed to imply 'structure that gets reinforcements'. Special forces guard posts do get reinforcements, so that's the correct name for them. Tachyon sentinels do not get reinforcements, so they have a different name.
However, the reinforcement placement logic is broken (mantis here
https://arcengames.com/mantisbt/view.php?id=18806) so that all regular reinforcements are placed at the command station. So, Wormhole Guard Posts should meet the definition but currently don't. Not sure if SF reinforcements are placed at the SF guard post or not, but they roam around so it doesn't matter as much.
Also, Pumpkin, SF guard posts used to have a much stronger impact on the SF's reinforcement budget, but at the time they also cost +1 AIP on death and weren't autotargeted. I think this was changed to allow the player to clear SF guard posts off human-controlled planets without cost, without creating a strong incentive to go kill every single SF guard post on the map.
Play with an AI using the Special Forces Captain type, or activate the Hunter plot. Or, for most !Fun!, do 2 AIs with SFC AND Hunter 10. Believe me, you WILL pay attention to the SF at that point.
A game like that is on my list, but at the rate I finish campaigns, it'll be a while.