Dwight,
Well presented.
The conclusion that DWM did produce 9mm P 08 s from 1927 to 1930 is simple and logically follows from the evidence you analysed.
Acceptance of DWM production in 9mm makes convoluted scenarios for explaining the s,t,u pistols un-necessary- as you ably point out.
I do believe from reading many threads and posts that some of us had already started accepting that the '29 Commercials as Jan called them could easily date to 1928-9, or 1930. Extending to late '27 is not much of a reach.
Thanks for your effort and writing.