I can confirm the 737CL sim behavior on single AP. In fact, during a sim session with a 25,000h something instructor which had flown everything from the -200 to the various NG:s, specifically showed us this feature as a nice to know in case everything else goes out the window. We actually did it SE if I remember correctly.
The reason why the FLARE mode wouldn't be armed seems quite obvious since this is not a certified procedure. Just because the graphic isn't there on the screen doesn't mean the AP isn't prepared for it.
On the question on trim req for flare or not, I think that the behavior of the AP system on the 757 gives a good clue. LAND2 - trim. LAND3 - no trim. This seems to be a question about the fact that this is a fail-passive procedure.
Any chance that someone knows someone at Boeing to get some insight on the tech side from the source?
I'll try to get hold of a former 737 technical pilot I know, who by my knowledge never been presented with a question about the 737 he's been unable to answer.
