Progressive v. Liberal?

Lately I have seen a number of article stating that Americans are abandoning the term "progressive" in favor of using "liberal" again.

This particular article is half a year old, but you get the drift (too lazy to search for another): https://www.washingtonpost.com/opinions/voters-reclaim-the-liberal-label/2015/06/19/feeca592-168e-11e5-89f3-61410da94eb1_story.html

What I don't understand -- and yes I am a Gen Xer who lived through the era in which the Republicans tried to turn the word liberal into an epithet -- is that the people who write these articles seem to think that progressive = liberal.

I have never understood it that way, and neither have any of my contemporaries in my sphere (yes, anecdotal evidence).

To us, "progressive" has always mean MORE liberal, MORE lefty, you know, people who want substantial, not incremental change. This is confirmed by the Congressional Progressive Caucus being the furthest to the left caucus on the Hill and the Progressive Democrats of America being the left alternative to the DLC.

"Liberal" on the other hand has always meant anything from barely left of center to more mainstream Ted Kennedy.

The term progressive has always been used in my world to distinguish from the more moderate left.

So why do they keep writing articles implying that the words mean the same thing?

Is this a Boomers think they are synonyms v. Gen Xers think they are distinguishing terms scenario, in which Boomers reverted to "progressive" because they were embarrassed to be "liberals" but didn't understand that to younger people, there was a difference? What do Millennials think?

What is your experience?