This is actually intended, like Blobs said, observers in bedrock detect block updates, not state changes.
Can confirm this affects Linux Mint 18.04, BDS 1.13.0.34, downloading the files in https://bugs.mojang.com/browse/BDS-46?focusedCommentId=517042&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-517042 just throws an error saying version "OPENSSL_1_1_1" not found, so I'm assuming dependency issue?
This is actually intended, like Blobs said, observers in bedrock detect block updates, not state changes.