I would like to return us to the topic of "pelure paper" specifically. In the privacy of our own homes we are free to use language any way we please, but it will not prove very fruitful for us to try here to reinvent a term which has already existed in the hobby for a very long time. Where to look? For those bound to books you can get some help from
Fundamentals of Philately (revised edition 1990) by L.Norman Williams, p. 61. He used an image on p.59 which gave me an idea for use here.
This is a scan of the backside of the Bowlsby essay pair shown earlier.Some of its coloration is due to the distinctive paper, but more to the fact that it was fully gummed.
Here is a detail of the inscription reverse:

To better understand what you are seeing, it is well to consider this definition of pelure paper from a Wikipedia page:
pelure - Thin, often brittle, semi-transparent paper and can be either woven or laid and is rendered semi-transparent by the resins used in the manufacturing of the paper. Stamps printed on pelure paper sometimes do not survive wholly intact because of their brittle nature. Pelure is easily identified because of its transparency. Pelure is a French word meaning skin or peel, like that of a banana, which is why sometimes this paper is compared to onionskin paper.
Please note these words: "
...is rendered semi-transparent by the resins used in the manufacturing of the paper." We will come back to that.
Here is a reverse side example of pelure paper which was never gummed for an essay by the Philadelphia Bank Note Co. The amount of detail visible
through the paper is most remarkable.

I have adjusted the contrast on that image, but here it is raw:

With this bit of background let us attend to the claims being made about the used stamps from the Continental Bank Note Co. being called pelure paper in this thread. By definition pelure paper is intentionally configured for special features by the use of resins added to the slurry in its formulation. It is thin and translucent by design and not mere happenstance. As such there is no evidence whatsoever that the Continental Bank Note Company ever received approval for the issuance of such stamps by the POD. Neither is there evidence that they used such specially formulated paper for proofing or essay design. Work of that kind by others does exist, but not for Continental in its handling of the stamp contract.
Various specialty papers were produced and tested in the U.S. in the 19th century, and some of these experimentals have survived. But each has a particular configuration that makes it distinct. The field is very broad.
However, with respect to true pelure paper for postage stamps, prior to 1900 no such stamps were ever approved for U.S. postage production. What then are we to make of the "thin papers" of the National Bank Note Company and what we are being shown here from Continental? The U.S. Specialized has long acknowledged that certain issues by the National Bank Note company (such as certain of the "E" and "F" grill stamps) were issued on "very thin paper." Here is a poor example of the 1c in ultramarine w/o cancel.

However, the paper on which they are printed is merely a thin version of the paper they generally used, and not specially treated as with the Bowlsby pelure paper tests. Recall that National had designed the Banknote issues for printing on a hard paper with a gelatin sizing agent so the design would stand out cleanly. Continental kept to this formula but with a somewhat less permeable quality. That is what was authorized. But even in its thin state it did not perform with the same level of translucency as is evident in real pelure paper.
It confuses the issue to apply to stamps not intentionally configured as pelure paper a term so specific as "pelure." Thin, hard paper, such as used by National and early Continental in production was never officially configured as "pelure" paper. Nor do those papers have the same level of translucency as true pelure paper.