SUMMARY
The video progress information is missing from program's icon on the panel, so integration with Plasma is not as good as it could be and it's also not good for some use cases

STEPS TO REPRODUCE
1. Play a video in windowed mode or full screen mode (on another screen)
2. Optional: Skip a bit ahead so it's a bit further away than the absolute beginning (to make it easier to notice the problem).
3. Look at the program's icon in the panel.


OBSERVED RESULT
Unlike Discover at least, (with downloading and installing updates) the player doesn't show the progress of the video playback in its icon on the panel.
I don't have any audio file at the moment, so I didn't test with that too.

EXPECTED RESULT
The player shows the video's progress.
So if:
1. You're playing a concert or music video minimized as you don't care to see the image that moment since you just want to listen.
2. You're playing a movie on an another screen, like a monitor or TV, which most likely is in full screen.

You should still be able to see the progress on that full screen movie on the main screen program's icon in the panel.

SOFTWARE/OS VERSIONS
Linux (Debian 13 - unstable repository)/KDE Plasma:
KDE Plasma Version: 6.3.2
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.12.17-amd64 (64-bit)
Mesa  Version: 25.0.0-1
Graphics Platform: Wayland

HARDWARE SPECIFICATIONS
Hardware: Laptop Dell Inspiron 5770 (17" 1080p@60Hz screen)
CPU: Intel® Core™ i5-8250U CPU @ 1.60GHz
GPU 1: Intel® UHD Graphics 620 (main, Vulkan capable)
GPU 2: AMD Radeon R5 M465 Series
RAM: 8 GiB (7.7 GiB usable)

ADDITIONAL INFORMATION
To better understand my use case at Home I have opposite to a sofa, near the wall, next to each other:
The desktop computer, then the 5.1 AV receiver, then the TV. AV receiver in the middle to get the sound passing through it.
With the desk and other supporting furniture there's considerable amount of space between my desktop monitor and the TV, which makes things hard to see on the TV from the computer's chair.
Anyway, with this setup I'm able to put from the desktop computer movies, tv shows and concerts and the TV as the screens are in extended mode and I just drag the video player window to the TV and double click on the image to make if full screen.

To be able to see the video's progress on the TV without bothering my family and friends for which I play the videos and also destroy their immersion, I need to easily verify the progress without going with the mouse to the TV and hovering around to see the progress bar.
That's also hard to do with the distance between the desktop computer that has the mouse and the TV which I see at an angle.
While I was using Windows 7 + MPC-HC this was easily to be done as MPC-HC was transmitting to Windows 7 the progress to color the icon accordingly.
Here on Linux, neither Haruna, nor MPV, or VLC show it.
But considering that Qt / Plasma has support for that as Discover clearly demonstrate it (and maybe other programs too, but I don't remember which. Nate also mentioned it years ago on its blog) and Haruna being build with Qt and a KDE program, this should be possible and very helpful to have, besides making the player more professional and integrated with Plasma.

Using the laptop's monitor to work on something while I have some video playback on the external monitor is another case that I have from time ti time and there too it's great to just look at the icon to know the status of the playback.
BTW, when the playback it's paused, it would be nice that besides the progress a yellow color will be shown to be more obvious at a glance that the playback is paused for whatever reason.  Or a red color if the last video from a playlist was reached and the playback stopped.
That would probably require going into Dolphin to change the folder, like the seasons of a tv show.