Only one reason I can think to swap 'Ukraine' with 'Russia' in captions: the Ukrainians are doing bad things to civilians, and they want Russia to take the blame. So for example, if you see a post of a Ukrainian jet bombing a civilian neighborhood (as I have), the captions would tell you the person filming was screaming that it was a Russian plane.

Since the media and politicians are all on the side of Ukraine, social media postings could mess up the propaganda. But given language issues, most in the West have to rely on captions to know who is doing what to who in posts coming out of Ukraine.