why generate output to tmp file and mv to actual file?

[John Calcote]

I recently ran across some sample code in section 19.4 of the Autoconf
manual (modified slightly to reduce example):

$(TESTSUITE): $(srcdir)/testsuite.at $(srcdir)/package.m4
        autom4te --language=autotest -I '$(srcdir)' -o address@hidden 
address@hidden
        mv address@hidden $@

This question isn't about autotest, but rather about the two commands in
this rule - why generate the output into address@hidden and then mv 
address@hidden into address@hidden
Is there some power mv has over autom4te that allows it better access to
the target under some conditions?

Thanks in advance,
John