Left Site Navigation

I have several sites and editing the site navigation on some are correctly in modern look . The 'modern' modern sites simply stay on the main page when editing the site navigation and are in the modern look as shown in "Good.png" below.

HOWEVER, other slightly 'older' modern sites (example one created 1/16/19) behave in old classic mode and take you to the old https://.../sites/.../_layouts/15/AreaNavigationSettings.aspx for site navigation as shown in "Bad.png" below. 

Before anyone askes, 'Yes, all sites are in modern mode. There's no classic mode implemented ANYWHERE and were all created as Team sites.'

So, why are these different and why are the older site's navigation method not being updated?? It's been 3 years, it is SharePoint Online after-all and there's nothing I can do or have done to make these differences. Is it Microsoft hasn't updated the navigation yet? I'm not going to create a new site and move everything over as MSFT don't have any tools to perform this function. 

Also, I have already asked this question in Support but as per usual there's never a straight answer just reiteration of your question then "out of office" announcements. Perhaps I'll receive a response (not an answer) sometime in April.

GOOD.png (new modern site navigation editing process)

BAD.png (also modern look site editing process, SUPPOSEDLY, on an older 'modern site (?)) 

Thanks