I've found myself needing to differentiate between a hard and a soft dependency for a task. It could be a simple icon, text color or some other visual cue in the Maniphest -> Task -> View -> "Depends On" list.
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Trees, large dependency lists, and all sorts of microscopic task organization isn't something I feel is part of our core philosophy. I do think this is something the product (Maniphest, Workphlow) will be opinionated about with the understanding not all customers would like a simplistic task management application - and I think that is fine. I think there needs to be JIRAs in the world where some corporate structures dictation large ginormous workflows, and there isn't anything wrong with that. It's not the direction I see Maniphest taking, specifically in the near term.
Functionally as you describe it, soft means it's something you can do regardless of being dependant on another task. So this, like I think @btrahan eluded to, means it's not actually a dependency. Even if it is in your corporation, it's confusing enough that it's not something we'd upstream.