You can have 4k60 and still have open office take seconds to respond to a keyboard input.
Sure but why include that if a text processor is too much for the board? To display static images or demoscene visualisations?
If it's hardware accelerated it could still display that fine. I'm sure there are older games that could indeed run in 4k60fps
It will probably display video at those resolutions and refresh rates just fine, so it could be used for improvised commercial displays like a TV at a conference looping some information, for example.
The Raspberry Pi 4 could do a single monitor at 4K/60Hz.