> Blackboards are not black, they are grey

Yes, and tennis shoes aren't only used for tennis.

What you wrote is not correct. First, I assume you are not making the technically-correct-only assertion that since everything, including Vantablack, reflects some light, it isn't truly black but only a dark shade of grey.

Quoting Wikipedia, "Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone". That's "black" and "dark grey".

But you don't need to take Wikipedia's work. We can look at books from a century ago and read a book where they improvised a blackboard using black paint: "This space was carefully sandpapered and immediately after received its first coat of black paint, prepared with oil, which served as a foundation. After 24 hours, another layer of the black color followed, (this time without oil) and finally, in two more days, the black brush completed, from every standpoint, a perfect blackboard." https://archive.org/details/jstor-3406078/page/n1/mode/2up?q...

Or the 1905 book "Nelson's blackboard drawing" which mentions "So long as the black surface of the board is visible, the sketch is quite conventional" at https://archive.org/details/b1625318/page/n121/mode/2up?q=bl... . (As an aside, there are some excellent chalk drawings in that book.)

Thus, black surfaces for chalk use in a classroom have long been referred to as "blackboards."

You can see the transition to "chalkboard" in the 1950s (emphasis mine in the following) in a 1955 publication saying "And don’t overlook the old standby, the chalkboard. Notice that we refer to it as a chalkboard, since it is not black. A green board and yellow chalk will not produce the halo effect that results from using white chalk on a blackboard. You can make a simple and inexpensive chalkboard by painting the smooth side of a piece of tempered masonite with green chalkboard paint." https://archive.org/details/CAT10679308/page/2/mode/2up?q=ch...

As well as in this 1953 newspaper article titled "Britain Bans Old-Fashioned Blackboard For The New Colored Chalkboard", wherein we read how "a slab of black on the wall has a tendency to create a dark, depressing, uncomfortable and gloomy atmosphere", and how they will be replaced "with a 'chalkboard' in some one of nine brighter colors" https://archive.org/details/1953-04-11-1953-04-30/page/n167/... .

The trend continues, like this 1962 comment that "The chalkboard (blackboard) is one of the oldest graphic or visual instruction devices. The earlier slate blackboard has now been replaced by white, green, or yellow satin-surfaced or glareproof glass or plastic chalk-board." at https://archive.org/details/audiovisualmater0000unse/page/66...

By the 1970s you can see Sears referring to an "old-fashioned blackboard" as a "black chalkboard" at https://archive.org/details/1970-1979-sears-wishbook-toys_20... and at the bottom of the page is a flip chalkboard with described as blue on one side and black on the other.

> So why is it that black is renamed on the grounds of accuracy?

As they said in the 1950s, "we refer to it as a chalkboard, since it is not black."

While your "hypersensitivity" hypothesis doesn't explain why the changing usage started in the pre-Civil Rights era of the 1950s, and including the UK.

> could you elucidate

I think you are hypersensitive to the idea that others are hypersensitive to using the term black.

I think you are so hypersensitive that you dismissed counter-evidence out of hand, without further examination.