Install LO 6.4.0.1. => There's a 'help' directory with ~50-80 MB media files and a bunch of generic/helper css/html/js/xsl files (no actual help content). This is a regression in 6.4 compared to 6.3. The installer is comparably larger because of the extra content as well.
Verified in a widows build in master, but I am not sure if this is not "working as designed". The full help is packaged with the main software.
Bug is still in 6.4.0.2. I don't see the help itself packaged with the main software, pressing F1 in LO opens a dialog that built-in help isn't installed on my computer, and prompts me to read help online. The extra content is really just a bunch of screenshots as far as I can see, some in several languages. Eg. there's a single 'help/media/screenshots/cui/ui/charnamepage/CharNamePage.png' image, but there are many 'help/media/screenshots/cui/ui/effectspage/<language code>/EfefectsPage.png' files.
Olivier Hallot committed a patch related to this issue. It has been pushed to "libreoffice-6-4": https://git.libreoffice.org/help/commit/191058eba782a34dad89959d5a20d6f2edd4bc3a tdf#129604 Place localized images in right makefile
The patch resolves part of the issue and build must have "--without-helppack-integration" to isolate the Help packaging from the main package. But still many media files are sent to main packages (screenshots/, files/ ) with no need.