Seatposts aren't tapered. This one was stuck because it wasn't lubricated on installation. But indeed, this is definitely a homebrew "fix". They took the stub of a narrower Sakae seatpost, and attempted to use the pipe as a "shim". But since there was just the stub of the original post going into the pipe, it was a (probably catastrophic) failure waiting to happen. Just as well you had to destroy it to get it out.