Interesting. I was not aware that was a thing. Orientation info seems way less useful in a lossless format like PNG. It makes sense in JPEG for instance because rotating and re-encoding would be lossy and slightly degrade the image.
The orientation data is defined as part of Exif. Both JPEG and PNG has officially supported ways of embedding Exif data. It's not defined specifically for PNG, but you would expect the Exif tag to work the same way regardless of image data format.
I dont think i would. Exif contains a bunch of metadata that affect the interpretation of image data in jpegs which dont make sense for pngs. I would expect exif in png would only be for metadata meant for humans like who the author is, not things that alter the display of the image.