I'm using LibreOffice 4.3.6.2 on Mac OS X Lion (10.7.5) on my old MacBook. Yesterday, my LibreOffice 4.3.6.2 says "You can update to LibreOffice 4.3.7". I downloaded 4.3.7 and installed it, but it cannot work on my MacBook. And I knew 4.3.7 requires Mac OS X 10.8 or later.:-) I think it's a bug that LibreOffice 4.3.6.2 on Mac OS X Lion (10.7.5) says "You can update to 4.3.7", don't you? I think checking update feature of LibreOffice should check between version of OS which it works on and requirement of new version, don't you?
Assuming this is true, and I have no reason to doubt, LO 438 is intended to the be last release of the 4.3.x line of the software, so unfortunately, you will be stuck with 4.3.7. I agree however that you should not be incited to upgrade if you can't because of the build type bitness, but as far as I know we only filter on the version number and not bit type. This report will probably get set to invalid as a result, not because it is untrue, just because no one will fix it.
32bit versions available here : https://www.libreoffice.org/download/libreoffice-still/?type=mac-x86&version=4.3.7