Indeed they aren’t in the tag pane.
But tags are actually displayed in the search pane even if they are in a code block.
Are you talking about Editor / Show frontmatter option that hide the frontmatter ?
Or are you talking about you not wanting to see a tag as a link in code blocks ?
The request is actually to not treat the yaml frontmatter as a code block. I would also don’t want links and tags in other code blocks.
Maybe a special code block syntax (like the mermaid one) used internally by obsidian would do the trick to accept tags and links in the yaml header.