Thank you to all who answered my questions, upon reading the linked articles I decided to file it under what I would call "practical superstitions" i.e. admonitions that were once very much observed to ensure safety, which now may or may not still make much sense:
Berlin (i.e. eastern Germany) was the seat of the government and the emperor so every new "fad" would start there. In those times living quarters would be cramped and the newfangled spring-loaded umbrellas might very verily have caused harm, because nobody was used to them.
Same as not walking under ladders btw: without roofrailings etc. and steep roofs, hammers and other things and persons might very easily fall off, so rather don't pass under ladders in those times.