It seems the 'page tree' macro does not use the current emoji for the pages displayed in it. Assumedly it's using the emoji that was used when the page was created? Not sure.
Here's a screenshot demonstrating the issue: all these pages have green tick emoji's on them: left side of pic = the standard confluence sidebar showing the current emoji. Right side of image shows a "page tree" on a different page where it's pulling the correct page names, but the page emoji's are a collection of old emoji's and no emojis... It's not even possible to have a page with no emojis anymore: everything should at least default to the "document" default emoji... So yeah, it's weird :D