"In 1937, the city, along with several towns in the surrounding Harburg district, was transferred from the state of Prussia to Hamburg under the Greater Hamburg Act. The city lost its independence one year later, on April 1, 1938."

when Greater Hamburg was created the new big city had probably many common street names like "Bergstr" mountain street - more than once and in some cases maybe 3 or 4 times.
so, its common practise in such city expansions to change such a double name a little bit from Bergstr.31 to Schwarzenbergstr.31. I have seen such changings more than once.