Not sure if this is a bug or not

So I’m doing an empowered monolith. I farm up the 800 Stability to do the boss. I noticed that one time I killed the boss and gathered my loot I hit my town portal and went through the portal and forgot to talk to the NPC after killing the boss. Went back to the thing to go do more Echoes thinking that I had to do more farming to get back to 800 Stability but noticed that I was still at the 842. So I did the boss again and he was there. Killed him again and got loot. So i figured I would test out using the portal and once again still at 842 Stability. Is this a bug or suppose to happen? If it’s not a bug seems a little broken once you get to a Corruption you’re comfortable farming at you can just take a town portal back and just rinse and repeat.