I am at a disadvantage in that I cannot see what ahrefs.com is reporting and what tool is used against what site or page.
Be that as it may. All of these tools MUST be taken with salt. Some with a dump-truck of salt. Some with a caravan.
Your question is in regard to the description meta-tag and
og:description and the fact that ahrefs.com is reporting that these should not be the same.
I am not a social media expert and cannot comment on how
og:description effects the various social media outlets except to say that it appears that Google+ uses it in some fashion. There may be a reason for Facebook that the description meta-tag and
og:description should not match. However, that does not seem to be the question here.
Google does not use
og:description at all nor can I see any recent or ancient mutterings in that regard. I did do a fairly quick search to see of
og:description may be picked up for the SERP snippet under any circumstance that I am unaware of and I cannot find one.
From a search engines perspective, it does not matter one whit whether the description meta-tag and
og:description match or do not match. And that makes sense. The
og:description is not content. Of course, neither is the description meta-tag, however, the description meta-tag along with the title tag has a long standing tradition of great value in search. So much so, that these tags alone often yield better results than searches against content. It all goes back to the original research paper published by Brin and Page back in 1997/8. Both tags are strong significant clues in the search game and not likely to be replaced easily.
Where the description meta-tag is replaced in the SERP snippet is when the search query matches a content segment and that match is a strong match. This of course presumes a weak match against the description meta-tag. Given that header tags are not matched in SERP snippets gives a strong clue that the
og:description would not be either. Plain and simple folks. The only two things on a page that is used for SERP snippets is the description meta-tag or content that is not a header and very likely within a paragraph tag.
It is extremely likely the reason why search engines do not pay attention to
og:description is low adoption. Low adoption signals unreliability for any data element. We have seen this with the author tag which failed miserably. If and when adoption increases, then this may change, though I doubt it.