Can't put it any simpler cass-hacks...
The meta description has no bearing on ranking within the search engine results. I said it, the blog said it.
The meta description can have a bearing on whether or not a page is placed in the SI. I said it, the blog did not say anything about it at all.
Duplicate meta descriptions can cause a page to be placed in the SI. Being in the SI can cause a page not to show up in the search engine results.
I'll say it again... It is being in the SI that can cause a page not to show up, NOT the reason the page in the SI.
Did the blog post say that a duplicate meta description won't cause a page to be placed in the SI? No. But because a page being in the SI can affect where it shows up in the search engine results, or if it does at all, you automatically leaped to the conclusion that because a meta description cannot affect the rankings within the search engine results it cannot cause a page to be placed in the SI either.
It is the high blood pressure that can cause a stroke NOT the reason for having the high blood pressure.
My analogy is just fine. The conclusions (cause and effect) you are drawing are incorrect.
As far as the title element goes, duplicating the title element within a site can cause otherwise completely unique pages to end up in the SI. You are of course welcome to test this and the meta descriptions yourself using a methodology you are comfortable with.
Additionally, you might try using a search engine to find additional thoughts and information...
duplicate meta descriptions - Google Search
Dave