I also noted that the parchment poll thread was closed, but while the topic is still of interest, I was thinking about starting a new one. In order not to create a hydra, I assume that it will be OK to use this one for the general topic.
The outcome of the poll isn't entirely surprising. In my opinion the particular question that it intended to answer was one not really suitable for a public vote by people without the appropriate background. The opinion of one person with such background would be all that is needed.
One of the typical problems of such a discussion is, that often the right answers are provided in some people's contributions, but these are simply not recognised as such by other participants, and the discussion continues.
The question about parchment and vellum, which people think was not answered, is a case in point, and Helmut's remarks on this topic basically summarise the situation.
In 2014 I had the opportunity to sit opposite to two interesting people at a dinner table, namely the parchment maker Jesse Meyer, already mentioned a few times as the one identifying the species from which the cover of the Voynich MS was made, and conservator Abigail Quandt of the Walters Art Museum in Baltimore. She is known for her work on the Archimedes palimpsest, but she was also one of the key people exposing the 'Archaic Mark' as a (relatively) modern fake. Joe Barabe of McCrone was another.
When I told them that I had a general question about parchment, they both immediately guessed that it was about the terminology vellum vs. parchment. And they were right
Even though they consider parchment from very different angles, and they had never met before, together they gave me a clear and consistent answer.
The etymology of the words parchment and vellum should be generally known I guess.
The first important point was, that usage has changed a lot over the years. In the past, vellum was used for parchment made of calf skin only. At times, it was also used for one of goat / sheep (I forget which) but not the other. It has at times been a point for discussion and disagreement among experts, and indeed, different parts of the world have adopted different definitions. In some areas, vellum was used to denote a higher quality parchment.
Since one may find all these different definitions in different places on the net, confusion is almost inevitable.
Abigail Quandt further clarified that, nowadays, the terms parchment and vellum can be used interchangeably in most parts of the world, though she cited the UK as an exception.
In neutral discussions, the term parchment can be used safely. I was happy to hear that since I had adopted that term for much the same reason on my web site.