SUMMARY
In double-click to open mode, single tap opens folders in Dolphin and Kate, but not all apps.
File Open and Save As dialogs in Firefox, Okular, perhaps others require double tap to open folders 

STEPS TO REPRODUCE
Set the system to use double-click to open folders
1. Open Firefox or Okular
2. Use the File Open or Save As dialog
3. Single tap on a folder

OBSERVED RESULT
The folder is selected

EXPECTED RESULT
The folder is opened, like it is in Dolphin or Kate's File Open / Save As dialogs

SOFTWARE/OS VERSIONS
Operating System: Solus 4.7
KDE Plasma Version: 6.3.80
KDE Frameworks Version: 6.13.0
Qt Version: 6.8.2
Kernel Version: 6.12.17-314.current (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFORMATION
I was testing a MR when I noticed this behavior, and replicated it on git-master
From a usability and consistency perspective, users of touch screens would prefer to be able to single tap in all dialogs where you can select folders, rather than only some