I am working on a web application, and we are focusing very much on the consistency of the look&feel. When we are designing tooltip styles, we can see there is the 'plain style' tooltip and all kinds of styled tooltips. Like the bootstrap one for example.
Below is the example of a plain tooltip:
Below is ab example of a 'styled tooltip':
It's very natural to think that on the same page, the same style of tooltip should be used, right? but actually Google Drive used both of them in one page, and very close to each other.
As the picture below shows, in the top right corner of google drive, all ICONs in group A will use the 'plain style tooltip'; whereas all the ICONs in group B will use the 'styled tooltip'.
Is there a likely UX reason for this difference?