How to disable picture-in-picture mode completely?

1. When Pausing video or tapping on the remote's touchpad on my system it simply brings up the small bar at the bottom, and while it shows the icon for PIP it requires swiping up and clicking to invoke it. Otherwise, the bar disappears after a few seconds.
2. Never had this happen and I do a lot of testing for the forum, nor have I seen other reports from testers or other users

I don't think there is a way to disable it, but if one doesn't use it it is as easy as not invoking it. If you are experiencing those issues then there may be another issue with your system. Make sure it is fully up to date with 13.4 and if so try a reboot. If it persists restore.

That is not picture in picture, that is a thumbnail to show where it was paused. That thumbnail also goes away after a few seconds.

I have been testing for over 10 years and take into account all kinds of scenarios in order to properly account for different use cases. Also, you can't possibly make a generalized statement to say that no other user has a hearing disability or only watches content in their native language/doesn't use subtitles. If this were an issue then it would be easy to replicate and there would be a lot of others experiencing it. Even if you were just to account for others who are in the same situation as you that would still result in a steady stream of reports, and at the very least numerous responses since this thread started.

The bottom line is that what you are experiencing is not normal behaviour, as I said above if a reboot doesn't fix it then you can perform a restore. I can understand frustration, but if your intent is to just argue your case, even when there is nothing to substantiate it, instead of trying to the next step suggested then there isn't much anyone I nor anyone on this user forum can provide and I will leave you to it.

You are certainly not alone. I recently sent feedback to Apple about this very issue. Yes ... the PIP icon does get in the way of the subtitles. But even more annoying is that it is far too easy to inadvertently invoke PIP when clicking the left/right side of the Siri Remote repeatedly to skip back/forward in 10 second increments. I too would like the option to disable the feature entirely. It’s by far the #1 usability issue I have with the TV app.