Kemper released an update a few months ago allowing you to select between 44.1-96khz so I assume it sounds best when the Kemper and interface are matched up.
the sample rate setting is only relevant for recording with SP/DIF.
As others said, I guess Space is the 'issue'. Space adds a very short ambiance that makes listening through headphones much more enjoyable.
Space is only present on the HEADPHONE output - unless you de-select the tick box "Space>HeadphOnly" in the OUTPUT menu, page 5/7.