The end result is you'd have httpd-2.0.52-x, and httpd-2.2-x, which would each have their own php builds, mod_perl builds, mod_auth-foo builds etc. It basically causes several packages to be built twice to accomodate one package, and it's been an effort vs demand thing.
I thought having loadable modules were supposed to ease this problem not make it harder.
I guess the 2.2 branch must be different enough to require all new modules to be built.