The image isn't truly rotated but the JPEG EXIF rotate option.
https://www.howtogeek.com/254830/why-your-photos-dont-always-appear-correctly-rotated/ notes this but uses Windows examples. Now you can find your own tool for Apple OS to look at the EXIF data to see this.
Also, please try rotating in Apple's own Preview:
A quick question for those with a better understanding of the MacOS system on a deeper level...
I used to be able to work directly in Finder to rotate images to the left with a quick-action service and keyboard shortcut. This worked well for ages but since the last MacOS update (10.14.6 supplemental) the image thumbnails are no longer showing their rotated state. If I QuickLook with the spacebar then I can see the image has in fact rotated correctly. Whats happening?
(I'm trying this on my MacPro 10.14.6 right now)
Things I've tried:
Trashing the Finder preferences file
Running CleanMyMac to clean out all caches etc
Gone deeper by running Onyx to clean more caches
Force restart Finder
This is really, REALLY doing my head in now. This works perfectly on my 2012 Macbook Pro so I do not have any clue whats going on.