The document written by Atanasoff in 1940, which I have mentioned in another comment, analyzed all the known devices suitable to be used as memories and it proposed the first kind of DRAM, made with discrete capacitors, as the best combination of low price and high speed.
However, during the war this document was known by few.
Delay lines were already used as analog memories in radars and from there Eckert and Mauchly took them and modified them to be used as digital memories.
Von Neumann learned about the delay line memories from the ENIAC team, but he did not like the idea, because serial access seemed too slow, so he proposed to use instead of delay lines the second kind of DRAM, with a cathode-ray tube instead of discrete capacitors. Von Neumann took the idea of using a CRT as a memory from the tubes used in video cameras for television, which used an analog memory to store the image after exposure to light.
So when the report was written, probably von Neumann was not aware of the earlier RAM used by Atanasoff in his computer, but he also proposed a RAM as being better suited for computers than delay lines. Von Neumann was proven right a few years later, when at Manchester Williams made such DRAMs with cathode-ray tubes, which were later used in many commercial computers, e.g. in the first generation of IBM computers, until the development of magnetic core memories made obsolete both the delay lines and the Williams tubes (until the magnetic cores were made themselves obsolete 20 years later, during the seventies, by the third kind of DRAM, with MOS integrated circuits).
The most important users of delay line memories were the early UNIVAC computers, because they had bought the failed company of Eckert and Mauchly, for their IP.