Every mob have a random spawn in their biome , location spawners are not their only way to appear in the world ( phisical spawners =/= locations spawners )
Dragon egg nest are location spawner that u can block how u did , but there is still their global spawn
: a 25% of their spawn every 20metters each 2 minutes in a 64mx64m radio

Here is where i take the info
https://www.reddit.com/r/valheim/comments/n3pn4g/enemy_spawning_explained/