When we select a group of users as the manager of a category (for example, group A), they can act on the topics of that category like a TL4 user.
Now suppose the level of trust of the user who is a member of group A is TL3. This means that it can move any topic from the other categories to the desired category first, for example, close it and then return it to the previous category.
We have not used this feature yet and I raised this issue based on speculation. Could such a thing happen?
Can anyone confirm or deny this?
Yes, that is exactly how the feature was designed.
You should not put a user as a category moderator of you don’t trust him/her, like all staff powers.
Yes, this is true, but there is practically no difference between being a category moderator and being a site moderator for TL3.
In other words, if TL3 becomes the category moderator, it has actually become TL4
Did you know you can remove the TL3 topic edit power in the site settings?
No, I forgot that 
I think you mean disabling trusted users can edit others in the site settings.
The ability of tl3 users to change titles, categories, and tags is a great help to manage the community. Especially in large forums where more than 1000 topics may be posted daily. But this good feature will disrupt the work of the category manager or in the future the tag manager.
I must say that automatically increasing the system trust level in users and increasing their capabilities is different from our trust in the managers we choose.
There are various ways to prevent the disruption of these two golden abilities, and I think in the future, Discourse should pay attention to them.
For example, I think with the following features, we can provide some facilities to some people with a little more precision.
Ability to give more detailed access to groups (such as changing titles)
With this feature, you can have better control over the selection of managers.
Automatically join users with special badges in groups (such as registering users who have been tl3 for more than a year)
With this feature, the system can control group members automatically.