It's not an obstacle but an obstacle type or obstacle spec. Don't misuse words.
Your commit messages were wrong.

Also, technically I would be surprised if your hypothesis was true, so please do
a small test to check if it is correct. Go to a new level, add a few obstacles,
add a few sign messages, save, copy the
ship file somewhere. Remove an obstacle type, save, compare the files, check if
the sign message was shifted ingame.