Hello,
I still think that twaindsm should be provided on all architectures,
today I found that the 32-Bit twaindsm.dll from TWAIN.org hooks up all calls to "GetProcAddress" to see if a DS asks for the address of "DSM_Entry" in "twain_32.dll" and give it the "DSM_Entry" in itself instead:
https://github.com/twain/twain-dsm/blob/master/TWAIN_DSM/src/hook.cpp