I have opened a case in Kevin Atkinson's GitHub after downloading LanguageTool's .txt that contains a list of missing words in the spellers.
Here is the case:
I have noticed that many dozens are missing in my GB fork and I will start checking/adding them tomorrow or Saturday.
In the US speller it is a chaos as most of them are missing...
For three or four years that I have been maintaining the GB speller and I have added ~29'000 words to it.
There were the days when I used to post in his GitHub thousands(?!) of words I added to GB that were missing in US, but Kevin would only add three or four from the huge list...
So, I have given up suggesting words to Kevin, and this is probably the last time I will do it.