Earlier quoted context omitted.
I have no idea what "fully developed passive conjugation" is, but my language is very old and I imagine very difficult for English speaker to learn. There is an example how fun it can be: http://www.lituanus.org/1987/87_1_04.htm
It means that every conjugation of an active verb has a corresponding passive form, as in your link: esąs - buvęs - būsįas versus esamas - būtas - būsimas . But that's underselling it a bit, because Latin actually had a full 3-dimensional matrix of conjugations: time-based tense (past, present, future), goal-based tense (completed or ongoing), and action (active or passive), with accompanying participles for each cas…
> every conjugation of an active verb has a corresponding passive form
If we're talking about individual verbs, this does not and cannot apply to any language; there are always verbs that for semantic or syntactic reasons cannot take passive forms. (Examples in Latin: "esse" [to be] has no passive because the passive form of "to be" doesn't exist even conceptually; "sequi" [to follow] has no passive because sequi is, from a strictly syntactic perspective, already inflected as if it were a passive verb.)
If you're talking at a more general level about whether the language offers the possibility of a passive form for every active form a verb might possess, that still isn't true for Latin -- and in fact, the very example you give is quite badly wrong.
> Latin actually had a full 3-dimensional matrix of conjugations: time-based tense (past, present, future), goal-based tense (completed or ongoing), and action (active or passive), with accompanying participles for each case.
Side note: in the traditional analysis, a Latin verb is inflected in five dimensions ("tense", "voice", "mood", "person", "number"). What you call "goal-based tense" is traditionally just called "tense", though I agree with you that it is a separate dimension and shouldn't be conflated with actual tense. In linguistics, this dimension is called "aspect".
Latin participles do not inflect for person or number. Despite what you say here, they also don't inflect for aspect. They do inflect for tense and voice, but of the six possibilities (past / present / future) x (active / passive), only four are possible in Latin -- the present passive and past active forms do not exist for any verb. [1]
(It's possible to make the argument that Latin participles do inflect for aspect, in that some participial forms (the present and the future passive) use the imperfect verb stem and others (the perfect and the future active) use the perfect verb stem. That makes the argument you're making here weaker -- instead of Latin offering four out of six participial forms, it would be offering four out of twelve.)
[1] But remember how "sequi" couldn't have a passive form because it's already formally passive? This opens up a possibility for the perfect participle: secutus can mean "having been followed", the normal perfect passive sense, but it can also mean "having followed", in an otherwise impossible perfect active interpretation of the participle. The "passive form, active meaning" state of the verb can be carried through to its participle.