Old Genius (Song Page Switcher) does not collect any data of any kind.

This extension never connects to any remote server. It simply modifies any request to a genius.com lyric page to add a parameter that converts it to the old song page design.

While you have to be signed in to genius.com for this extension to work, this extension does not interact with any account data. Genius simply does not allow non-signed-in users to access the old song page.