Ah ok. Thank you for the quick reply. Sorry it took me a while to see. I tried adding them to a vanilla district style, where they didn't want to show up. But after trying a bunch more buildings on the workshop this is just generally broken in the game for office and commercial zones it seems.
I suppose that's why people have created mods to handle this instead :p I will try that.

I'm afraid I don't fully understand your issue. These buildings are not tied to a specific district style. They are generic growables. If you want these assets to show up as a district style, you'd have to create your own style using mods (but I don't know how that works).

For some reason these all show up as missing in the vanilla district style manager. (Eventhough they do show up in assets)