RX1 Clear Image Zoom
I have RX100, not your camera, so things may be different, but, the essence of it is: reduce the # of pixels to get additional zoom.
I like the feature a lot, and posted a full set of 'extra' zooms samples on the forum here:
much discussion of this occurred when the rx100 was new. Basically, those using RAW and doing PP have no use for it, while many of us who shoot jpeg and avoid PP like it.
As for shooting from afar and cropping later, that does not always give the same result, consider the specific light metering and focus area while 'extra' zoomed, compared to what metering and focus you might get from a wider shot.
If I have my camera on movable spot focus area, or center focus area, when I pass the end of optical zoom, into 'extra' zoom, it changes to multiple focus area, but, the metering will be based on what the sensor sees, which is the closer view of the subject.