It doesn't work for me. Though I set up seperate triggers first to move the spawn (which also moved the player character) then I ran back to my switch an then moved the waypoint to the spawn but it didn't drag the main character with it. Most likely when you moved the spawn point you were moving the character directly, nothing to do with moving the waypoint to the spawn.
You can use spawns to give tagnames to entities, unfortunately they are still stripped when reloading a game after visiting the world map or using the goto mission command. Though you can probably get around that by using a different tagname for every map. But every entity that passes through that spawn will get the same tagname (all your squad members and vehicles) and when using the move unit command either to move the character or move an object to the character the spawn point is figured into the equation. If the tagname is given via the spawn point then the move unit command will move both the character and the spawn point*, but if an entity is being moved to the character it's as likely to be moved to the spawn point as the game has to decide between two targets. I'm not sure how that would affect the give item from npc to human command.
*If more entities than just the main character used that spawn, including vehicles, then there needs to be plenty of room around the target waypoint, to spawn everyone. Otherwise the game will randomly choose to move only some of your squad and or the spawnpoint.