How is his floor a 4C? He can do everything proficiently at -
at worst - a 3C level and most things at a 2C level and some things at a 1C level. Even if you are skeptical of his ability to score 55+ points, that is not true 2C production. Low-end 2C production is 38-42 points which a guy with Jankowski's vision, hockey sense, skill, size, skating, forechecking, and lane-reading ability could do in his sleep.
If everything possible went wrong in Jankowski's career he would
still be a better hockey player than average 3Cs like Matt Stajan, Riley Sheahan, Ryan Spooner and Lars Eller.
His floor is a Sean Couturier / Nick Bonino tier low-end 2C. Guys who would only be 3Cs on stacked 1-2-punch teams, but are 2Cs. He actually skates better than both those guys, though. His ceiling is much higher, althugh Couturier hasn't hit his own ceiling yet.
But the common definition of blue-chipper doesn't just mean "really good prospect," though. Nor even "can't-miss prospect." It specifically refers to pre-draft consensus, and the prospects who are heavily scouted when they're younger, and are seen as locks to be immediate impactful players by just about everyone.
Think about how the term relates to blue-chip stocks, where it was borrowed from. A company can't just be called a blue-chip stock because it is trending upwards.
Here is the definition of blue-chip:
blue-chip
ˌblo͞oˈCHip/Submit
adjective
denoting companies or their shares considered to be a reliable investment, though less secure than gilt-edged stock.
of the highest quality.
"blue-chip art"
In 2014, while Gaudreau was a prospect, a team in need of an impact player the year afterwards would be very smart to trade for him (investment). They would still be trading for a prospect, but it would be a safe investment given we are talking about a guy who had dominated every level he had ever played at including the World Championships (to go with a nearly-exclusive 20-year-old Hobey Baker, NCAA championship, USHL rookie of the year, USHL championship).
If Gaudreau were not a blue chip prospect, Hartley would not have reserved a roster spot for him.
I disagree that it is a term reserved for draft day only. An example of a non-Flames blue-chip prospect to me is Sam Steel. He wasn't drafted high, but at present he is very much a near-lock to be an impact NHLer. Maybe not a star, but if your floor is a top six forward, which I think is fair to say about Steel, then you are blue chip. Or a year ago, Sebastian Aho... definitely a blue-chip prospect a year after his draft. Another one is Charlie McAvoy, he wasn't a blue chipper on draft day but he is now.