It should definitely be fixed. But Sling is right. It’s in no way related to SU8. Not even remotely. This bug has been a thing since launch (probably even since alpha) and was reported many times. Then the threads died a slow death and got locked because no one cared enough to push the issue.
Until your GTN was released and became popular, this was considered a “niche” issue that only affected a small subset of cockpit builders. It’s only really something that came to light in the last little while as people started realizing you can use tablets and touch screens with popouts, particularly with your GTN. And now it’s getting a little more widespread attention.
And not only does it not work right, but they added another bug in SU6 when they “fixed” mice not always working right in popouts. That’s the second issue you mentioned. Since SU6, touching a popout (like the GTN) moved to another monitor will register touches in the main sim window as well. So trying to work your GTN750 on Touch Monitor #2 will be registering touches in your virtual cockpit on Monitor #1. This can potentially flip switches, open the storm window, etc. So you’re correct the 2 issues are related, but they have nothing to do with SU8.
As I posted on your Discord last week, this bug in the sim is the only thing that has me using the TDS GTNXi over your GTN750 (despite owning a lifetime license for your GTN). I would really love to see this issue fixed. I’ve been bringing this up constantly since the first days after launch. But it would appear this issue isn’t on Asobo’s radar.
A few examples of reports of this issue since launch (first dating from Aug 20, 2020).
https://forums.flightsimulator.com/search?q=touch%20screen
It’s a known issue by a small part of the community. I’d be amazed if this is even on Asobo’s radar at all.
EDIT:
Here’s a link to the barely alive wishlist thread that’s managed to somehow stay alive since Sept 2020. over a year, it’s only managed to garner 84 votes.