This may be of interesting to some people. In 2022 a report was prepared estimating the number of horses in the park https://www.environment.nsw.gov.au/research-and-publications/publications-search/a-survey-of-the-wild-horse-population-in-kosciuszko-national-park and estimated the numbers at about 19,000 with a 95% CI of 14,500 to 23,500. I don't fully understand the methodology but it looks like a correct application of the technique.

Last year a group that are against the cull released this document https://meetourhorsemeat.com/wp-content/uploads/2023/05/Independent-Biostatistical-report-into-the-counting-of-wild-horses-Claire-Galea.pdf

In my opinion this is not very well done, and I believe the author suggested elsewhere that there were probably only 3,000 horses. The cull has now been in progress since sometime last year, and the current number culled is about 8 or 9 thousand.