1) the rendering of the OpenCycleMap is not such a great argument, that had already many other problems in the past and IMHO an oneway:bicycle=no would not necessarily need any markings so this is first of all a bug of the OpenCycleMap

2) but like Kevin said, many times there are actually markings, at least as shared lane, like here: https://www.mapillary.com/app/?z=19.809686532448527&lat=48.18893611111099&lng=16.370963888889037&pKey=1394005871031089&focus=photo&x=0.48577229844253345&y=0.6506645048407272&zoom=0

https://wiki.openstreetmap.org/wiki/DE:Tag:cycleway%3Dshared_lane

3) and finally: it's good practice to not change the tagging style without contributing anything new. In this changeset 149 cycleway:left=no + cycleway:right=no were changed to cycleway=no
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            Published using OSMCha: https://osmcha.org/changesets/133990070
            