I am seeing that the Attribute Table and the Attributes pane show GlobalID differently. One is all upper case and one is lower.
I would call it a bug.
ArcMap has them all capital letters in Attribute pane, Attribute Table, and Identify Table.
I would agree with you.
I don't see this in a dev build of ArcGIS Pro 2.5:
Just tested in ArcGIS Pro 2.4.0 and didn't see it as well:
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