The beat cop who saw a man resembling 'Kosminski' with Eddowes -- thus shoehorning this suspect into the 1888 investigation prior to his sectioning -- is Macnaghten's attempt to remove a man who resembled Druitt, or was Druitt as far Mac understood it.
In the official version of his Report, he could just blithely claim to his clueless Liberal masters that there were no witnesses, period.
But to Griffiths and Sims with their great interest in the case, especially the latter, he would have to assume that they might recall a top witness who saw a young, Gentile-featured man chatting with a victim.
He knew that Sims might recall that there had been a witness and of a Jack the Sailor' suspect (hence the 'confrontation' with Sadler, a Gentile Sailor) so he cheekily inverted the ethnicity of the witness and suspect.
It is in 'Aberconway', and therefore in 'Mysteries of Police and Crime' of 1898.
Sims never claimed to have actually seen this 'Home Office Report', hustled to him quite deceitfully as a definitive document of state, but Griffiths did, and it may have been conveyed verbally to Sims by Mac as well.
For though the is element is in Griffiths, Sims had something new to add in 1907; that the cop later saw this Polish Jew and thought he somewhat resembled the Polish Jew.
In my opinion, Anderson reading this remembered correctly that the witness was not a beat cop but a Jew (Lawende) but then he retained the incorrect element of Sims' tale: of suspect being a Jew as well: 'Kosmisnki'.
The story of Anderson's slam dunk witness confrontation, seemingly confirmed by Swanson in private, does not appear before 1907 -- before Sims' big piece.
Quite inadvertently, I think, Macnaghten set in motion the notion of the Polish suspect being seen with Eddowes and thus seen by a Jewish witness.
It is just a hop, skip, and a jump for a failing memory, one pained by the whole matter, to misremebering the Sadler confronation with Lawende, not by confusing those two suspects, as detractors of this theory often counter, but by doing what Mac-Sims had done: substituting one for the other. eg. Sadler does not exist anymore. The evenjts of 1891 do not exist anymore, just as they do not in the Sims' piece.
For here we have two sources: Sims in 1907 with the un-named 'Kosminski' placed with a victim in front of a witness, who then confronted the witness sometime later -- in this care a fictitious beat cop.
We have another 1891 press source which shows that there was a Jewish witness -- Lawende again -- who confronted a Ripper suspect, and the result was disappointing.
The policeman witness and 'Jack the Sailor' become arguably fused with 'Seaside Home'; a police location by the sea at which a witness confronts the Jewish suspect. With a disappointing result.
But, it's all ok, because hthe swine was sectioned and then dead.