Steps to reproduce the issue

Create any menu with a tag.
Example recepty.mobi/postnye-retsepty.html

Expected result

By entering:
/postnye-retsepty/fsdkljfsd
/postnye-retsepty/total-garbage
/postnye-retsepty/abcdefgh

The pages are available and duplicate the page: recepty.mobi/postnye-retsepty.html
There should be a 404 error when I enter:
/postnye-retsepty/fsdkljfsd
/postnye-retsepty/total-garbage
/postnye-retsepty/abcdefgh
But for some reason it’s not there, but a duplicate is triggered.

Actual result

Page
/postnye-retsepty/fsdkljfsd
/postnye-retsepty/total-garbage
/postnye-retsepty/abcdefgh

200 Ok and duplicate the page /postnye-retsepty.html

System information (as much as possible)

Joomla! 5.1.0 Stable cgi-fcgi 8.3.1

Additional comments

I tried on many sites, the problem exists. Does anyone know how this can be solved?