Today scan functions were bypassed (see bug 92478) in 64 bits Windows version.
I use for photos irfanwiew 64 bits and i see it is able to scan with TWAIN or WIA interface without problems
So with task manager i have checked what process it starts for scanning
in fact it is simple when scan is started:
irfanwiew 64 start a 32 bit stub which control a 32 bit subprocess which contains portion of irfanview 32 bit code dedicated to scan functions
Why not use same method in 64 bits Win LO start a 32 bits stub which use portion of code 32 bits win LO which control scan functions ?
I think this is only method because Windows does not provide 64 bits TWAIN interface
Rereading tdf#92478, I noticed 2 things:
1) this tracker could be a dup of tdf#101066
2) https://bugs.documentfoundation.org/show_bug.cgi?id=92478#c29 advices to retrieve TWAINDSM.DLL, perhaps you can give it a try?
Another interesting comment here:
64-bit TWAIN 2.3 drivers for Windows are not widely implemented. While we've added support to use TWAINDSM.DLL 64-bit driver --in practice we have no Scan support for 64-bit Windows builds.
Implementing support for 64-bit WIA framework would allow use of widely available 64-bit scanner drivers. 
32-bit TWAIN drivers remain common, but providing 32-bit WIA should probably be implemented as well. WIA is stable enough on Windows that TWAIN could be deprecated.
*** Bug 106770 has been marked as a duplicate of this bug. ***
*** Bug 101066 has been marked as a duplicate of this bug. ***
this should be Windows only, TWAIN would remain viable for macOS and Linux
*** Bug 111407 has been marked as a duplicate of this bug. ***
*** Bug 114635 has been marked as a duplicate of this bug. ***
A pointer to a one-function-does-it-all for potential implementers: