The Nether portal is still active after I destroy it, set my respawn point in the nether and destroy the respawn anchor.

So I'm doing a challenge from my friend where I start MC in the nether. So I get a respawn anchor, and head in. Then I break the portal, obsidian and all, and go into survival mode and is about to place the respawn anchor when a piglin attacks me. Then I realize - the portal is still there! I go in and go into the nether, and the portal has suddenly reappeared. This is kinda cool, because you could farm obsidian this way, as long as you have a diamond pickaxe.