If you have Discovery Tree enabled all of Rubia's tech's seem to bypass being hidden and show up regardless of what Discovery Tree settings are.
https://mods.factorio.com/mod/discovery_tree

It makes it look like Rubia has no pre-requisites, which is confusing.

Also since only a small handful of techs are visible at once, this causes Rubia's question mark techs to flood the tech tree and requires a lot of parsing between what is actually possible and what is part of Rubia and irrelevant until I reach the planet.

Thank you.

Thank you for the report, but this is not a bug. Before, discovery tree would mess with Rubia's tech hiding, causing the mod to be unplayable. As a result, Villfuk and I worked together to program a blacklist in Discovery Tree to allow Rubia to tell Discovery Tree to ignore Rubia technologies.

I understand it is confusing, but we really don't have a better solution because of how Rubian tech hiding works. There will be at least one tech at the top with no prerequisite, and I chose to limit the blacklisting to just Rubian technologies. It is possible to have a more advanced system in the future because the experimental branch has a new way to hide technologies, but we're not quite there yet. Sorry.

Thank you for the context and taking the time to reply.