Map completion problem : bug or am I missing something?

Hi, I have problem with understanding how map completion is done and wondering if it's bug or not. I ran a Bazaar map. On Atlas, it read "kill boss of corrupted rare version of this map". I had pile of Bazaar map I got from running Colonnade, however I just want to run it without completing the map to avoid the Bazaar map dropping from running maps in other areas.
So I ran a Bazaar map, rare, but 'not corrupted. (simply used orb of alchemy, and did not use vaal orb). After killing the boss of the map, Atlas shows that the map (Bazaar) is completed, which costed me a cartographer's seal. To try to test this, I used cartographer's seal to uncomplete the map, ran a Bazaar map with rarity of magic (blue one), killed the boss, and the Atlas still tells me that the map is completed with the check mark checked.
Is this a bug? or am i missing something about how map completion works?

If you kill the boss of a map, regardless of the rarity of the map, it will show as completed.