Steps to reproduce the issue

Create a menu item, based on tags.
Choose 2 tags.
On the Selection menu, choose Match All, and choose Include Child.

Expected result

The menu will list those items that have both tags, or the child tags of the listed ones.

Actual result

The menu acts as if it set to Match Any & Include Child. It lists every item with either of the listed tags.

System information (as much as possible)

Joomla 5.1.0
Multi-language site

Additional comments

It seems to me that there might be also problems with menus based on tags, when only one tag is selected.