This is NOT a regression. Tested In //UE4/Release-4.27 at CL18319896
Printing an actor's transform as a string returns transform and rotation with a colon, but returns scale without.
The Log Reads: "Translation : X Y Z Rotation : P Y R Scale : X Y Z"
The Log reads: "Translation : X Y Z Rotation : P Y R Scale X Y Z" Scale is missing a colon.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-165125 in the post.