I agree that single vision os often fine for cycling
at least it is for me - in fact even for reading I often find myself looking at the book (OK Kindle) through the top part anyway
I only deliberatly use the other bit for small print and the like
Hence, for cycling I could even get the cheap one you seen advertised on the telly if my main concern was damaging my main specs
and then I would have a backup - which does worry me when we go on holiday - especially if it involves a lot of driving!