The 32 bit Linux build seems ok for those who don’t care to try to build it themselves. It’s only a few percent slower than the 64 when built right.
I guess that flag was put in for old 32 bit machines that might not have sse2. Unfortunatly there is no such thing as a 64 bit x86_64 without sse2 so the conditional compilation produced an empty body which did exactly nothing.