Certain rooms are flagged as exploration points and assigned XP based on the author/coders discretion. All you need to do is enter the room. You won't get any observation XP if you never look at anything. If you look at a PBF Statistic page for anyone it shows how many Exploration Points they found. That just means a certain room that was flagged with exploration XP.

You will pretty much always leave XP behind; don't get too hung up about it. If you explore an area you will probably get ~75% of the total XP for that area, as a rough guesstimate. Some exploration/observation points are extremely hard to get, thus why they are given rewards for finding them.