As far as I can tell @Midnight_Voice they are in UHD, I don't think the Pro Box is upscaling or if it's even capable.
Searching for UHD using the iPlayer app on the Pro Box returns UHD programmes, but the UHD logo is missing from the programme tiles. I think if anyone has a smart TV then they're better off running the apps direct on the TV, they just seem to run better.
Just to confirm that a search for UHD on the Pro box app and the TV app produces the same programmes.
One observation.
I suspect that iPlayer displays UHD in top right corner for a collection (often one or more series and sometimes extra content) only if ALL programmes in that collection are in UHD. So for example Blue Planet II collection does not have UHD displayed at collection level but if you expand the collection the 7 individual programmes do have UHD symbol but the Oceams of Wonder (extra programming for the series) does not. Similarly Champion collection does have the UHD symbol on the collection tile but if you expand the tile all the Series 1 (8 episodes) are UHD but the Extra for the collection "The music of Champion" is not UHD.
For Blue Planet II for example, the iPlayer app on the Pro Box does not have the UHD symbol at episode level at all, but it does on the TV app.
SAS Rogue Heroes has no UHD symbol at either collection or episode level on the Pro Box app but is tagged correctly on the TV app.
@Andy005 I see SAS Rogue Heroes with UHD symbol at both collection and episode level currently on PRo Box set in IPlayer Beta mode.
My T4000, if set to output UHD and given an HD Programme on the iPlayer to stream, will output UHD to my LG TV, where I can see via the Info button that the TV is receiving a UHD stream.
So this must mean that the T4000 can upscale, and it would be rather odd if the Pro box had lost this capability.
Conversely, my T4000, if set to output HD and given an HD Programme on the iPlayer to stream, will output HD to my LG TV, where I can see via the Info button that the TV is receiving an HD stream, which it must now be upscaling for itself.
I think my TV can upscale better than the T4000 can, but the T4000 can certainly do it.
Though none of this necessarily invalidates anything you wrote above; it just gives us one more possibility to consider.
That's odd @zulu17 , I've just checked the app on my Pro Box again and SAS Rogue Heroes does not have any UHD labels on it. I also checked that the app is in beta mode.
If I use the TV app, switching beta mode off makes no difference ie UHD programmes still appear and I can still play the test loop. So my assumption would be that UHD programmes are now part of the standard player, I don't know if that's true or not but it's what I'm seeing.
I played the same short clip of SAS Rogue Heroes via the Pro Box and the TV app and I couldn't see the difference, so I'm still thinking that the Pro Box app is just missing the UHD label. Why it's on some Pro Boxes and not others is the question.
@Andy005 Are your TV and Box Pro IPlayer apps at a similar version level .
For IPlayer the system information for these devices is found eventually if within IPlayer you select Settings>Settings & Help>Help>System Information.
A general observation about search within IPlayer eg for UHD. Is that the search results returned seem to be currently limited to 9 so you are not getting a complete set of results.