UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36

Example URL:
https://www.cms.gov/cciio/resources/fact-sheets-and-faqs/womens-preven-02012013.html

Steps to reproduce the problem:
1. Navigate to above URL 
2. Scroll down near bottom of page and note the links under the final paragraph of content
2. Hold down the Command key (Mac) or the Control key (Windows) and click on one of the links

What is the expected behavior?
Links should open in a new tab, just as they do with a right-click and "Open Link in New Tab."

What went wrong?
Four out of five of the links open in the SAME tab.  The fifth link always opens a new tab, even without Cmd-Clicking.

On other sites, the behavior is slightly different - sometimes the same action will cause a link not to open at all, or to be blocked by the popup blocker.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? No Safari (9.1), FireFox Mac (45.02)

Chrome version: 49.0.2623.112  Channel: stable
OS Version: OS X 10.10.5
Flash Version: Shockwave Flash 21.0 r0

In all cases that I have tested, right-clicking and choosing "Open Link in New Tab" works fine.  The documentation at https://support.google.com/chrome/answer/157179?hl=en implies that Command-Clicking and right-clicking to open in new tab should be identical.  

I have noted that Safari and FireFox behave the same way, and I'm sure this is a JavaScript issue of some kind.  My question is fundamentally, why does right-click "Open Link in New Tab" ignore the JavaScript and function correctly, while the keyboard shortcut does not?

It's a poor user experience to sometimes get the desired behavior (link opens in new tab) and sometimes not, depending on the whims  and design of a particular website.  The inconsistency is maddening.