the second attempt, we detect that it is a resource JBTM knows about so it uses XAResource.TMJOIN (I can't actually see that message in the later logs).
Note that the comments like "[TMNOFLAGS]" and "[TMJOIN]" were added by hand to the log summary you were looking at, whereas the log summary in post #11 is "raw" and contains no such hand-edits.
In the log summary (tempm.txt) from post #11, the TMJOIN operations are still there (2097152 is TMJOIN) -- the first one is:
in:xaResourceWrapper2.start(xid3,2097152) #6 @1362075193148..1362075193161
out:XAResource.start(xid3,2097152) #6 @1362075193152..1362075193157