procedure doesn't work on a natural spawning structure

i am trying to make a entity spawn with a structure, but it works only with structures spawn using a structure block, natural spawned ones don't work.

pls help

here is a video for demonstration:

https://u.pcloud.link/publink/show?code=XZwgk25Z9SB19Ki9FD5vp36GktRcv5U…