Gotthard Deutsch, Divine and Writer, Dies of Pneumonia’, 21 Oct. 1921, American Jewish
Archives (AJA), Cincinnati, OH, MS-123 Oversize Box 313; Chicago Rabbinical Association, ‘Gotthard Deutsch Memorial Resolutions’, 31 Oct. 1921, AJA MS-123 1/17.
An obituary calling a Zettelkasten "mere chips from his workshop" seems more indicative of the lack of knowledge of what one is and how it is used than a historian of information or academic with knowledge of the tradition calling it such.
This quote from 1921 is also broadly indicative of the potential fact that the idea of zettelkasten for academic use was not widely known by the general public, if in fact, it ever had been.