this went on "realists study re-assembling a Kalashnikov".

There was lots of English, obviously, but also a lot of adaptation and modifications. Almost nothing (in wide use) was copied identically so I don't think this is a 'simple explanation' why this machine is the way it is. If I were to guess - this is a fairly late, specialized, small-run device made by a DDR space research institution. Maybe they were more geared up to make 'international' equipment. Maybe that's just the buttons they had on hand. The device was also intended to be used in 'friendly' countries so that might have been a factor. It's also possible this was considered more unobtrusive - on the museum site linked in the article there's a Soviet spy field radio with English markings, for instance, for use overseas.