Enabling allow and deny rules to top-domain only

Prerequisites

[x] I performed a cursory search of the issue tracker to avoid opening a duplicate issue
- Your issue may already be reported.
- [x] I also searched the existing issues at https://github.com/gorhill/uMatrix/issues
[x] This is not a support issue or a question
- Support issues and questions are handled at /r/uMatrix
I tried to reproduce the issue when...
- [x] uMatrix extension is wholly disabled or not installed
- [x] uMatrix is the only extension
- [x] uMatrix with default lists/settings
- [x] using a new, unmodified browser profile
[x] I am running the latest version of uMatrix
[x] I checked the documentation to understand that the issue I report is not a normal behavior
[x] I used the logger to rule out that the issue is caused by my ruleset

Description

I'd like to be able to apply a rule only to the top-domain (or a sub-domain excluding descendants). This is more of a feature request. I am aware that the issue I describe is documented as normal behavior (I think in the "popup panel" part) and I was wondering if there is any technical, ethical (or otherwise) reason to this behavior and if a change could be considered. There are many cases in which I would like to allow for example a script from the top-domain to run without allowing sub-domain scripts to run (and I can't think of any examples in which denying top-domain elements without denying sub-domain elements would be useful, but I'm sure there are), this would help in enforcing a true "block all/allow exceptionally" policy.

A specific URL where the issue occurs

Steps to Reproduce

Allow/deny a top-domain element (script, xhr...)
All sub-domains' element get white/blacklisted

Ruleset

Supporting evidence

Your environment

uMatrix version: 1.4.0
Browser Name and version: Mozilla Firefox for Ubuntu canonical 79.0 (64-bit)
Operating System and version: Ubuntu Linux 5.3.0-62-generic

uBlockOrigin / uMatrix-issues