As you say in that section, "Open source licenses usually grant users permission to use open source software for any purpose." These source-available licenses (SSPL/BSL) are not open source exactly because of that: they place restrictions on users from using the software for any purpose. For example in the case of SSPL, it includes purposefully draconian language in the license that basically means that it can't be used freely to provide a "service". These kinds of "poison pills" obviously stop you from using the software for certain purposes.