I've been checking bug report threads and it looks like the dev is fixing things but has stopped renaming threads to mark them fixed. Are you sure there are major bugs left unfixed?

You might know more about that than me, considering one of the latest (still unresolved) bug reports was yours to begin with lol

First main issue I saw was going 6 months without an update (with several bug reports during the meantime). Not marking things as resolved or not makes it difficult to tell, I can't even be sure if this bug (originally reported on the All Planets Pack) has been fixed. UPS concerns from the same user was another significant factor.

And while not related specifically to "unresolved issues" (which I kinda used as a blanket statement), another reason for excluding it was simply due to balancing issues, taken from feedback from players on the Foundry discord.

As a third source of information, I used Loup's Guide to the Galaxy for reference, as they specifically call out Tiberium in their description, under the Comically unbalanced section, and these echoed the same sentiments I gathered from the Foundry discord.

Some mod planets are so unbalanced that they are actively detrimental to a playthrough (with other planets). e.g. Tiberium.

For a modpack that is advertised to be more streamlined and playable, it was necessary to make certain cuts, and Tiber didn't make it. Of course, just because it's not included by default, doesn't mean players can't add them in by themselves. It's also still included in the full version of the All Planets Pack; there are still plenty of players who use that version instead.

The balance concerns are understandable. You can use Tiberium to trivialize many resources once you've created a large enough patch. It creates a lot of pollution but that doesn't even do anything on most planets... I had to do a little digging to find out that you could use quality prod modules to make mass amounts of legendary quality resources via the transmutation recipes holy moly. I didn't think about UPS concerns, I should probably check to see what planets are using the most CPU in my game.
Cutting Tiber from this pack specifically makes some sense as well since here Tiber has tiberium and nothing else and that felt kinda boring. I'm not actually utilizing the planet at all after I researched its tech tree, and tiberium weaponry doesn't seem too useful (aside from, apparently, tiberium damage piercing all astroid defense wtf)