And the MAJORITY of cycle infrastructure IS mandated by signs 237, 240 or 241 normally by sign 237 
(240 and 241 are 'shared path' indicators but again mandatory.
Sign 240
Unlike the UK where it simply shows the presence of as cycle lane, in Germany it MANDATES ITS USE.
I thought that you would know this from your extensive, abeit totally flawed, knowledge of European cycling infrastructure and the relevant legislation.
Do keep up!