It seems that angle orientation for data defined label rotation is different in QGIS 2 (anti-clockwise) and QGIS 3 (clockwise). I mean angle values that are stored in the defined field when modifying label orientation with the graphic tool of the label toolbar. Is this intentional ?
Label rotation is applied counter-clockwise, symbology rotation is clockwise.
I'd like to alter the labelling behaviour so that rotation is applied clockwise to match symbol rotation.
If we allow project breaks for 3.0, this should be an easy fix. If not, rotation would have to be upgraded with projects to 3.0 to reverse the label rotation angle.
So yes, it is intentional and the fix can be seen here: