Product filtering by availability works incorrectly, both “stock” and “sale”. Filtering products does not hide variants that the filter does not apply to. This applies to both Widgets and filters. I saw that this is reported as a new feature, but maybe it should be reported as a bug?
To assist you in the best possible manner, I kindly ask that you please provide me temporary wp-admin info (wp-admin URL, username, password) to the Private Content area, this will allow me to thoroughly investigate and address your concerns more efficiently.
Also, please record a short video so we can reproduce the issue.