From my understanding, block properties should be mimicked to the best of the mod's ability? But when adding a block group containing bedrock, the generated ore will still be breakable and not, as expected, unbreakable.

Fixed in 4.6. I'll upload that soon and it should get approved by Monday.

This is a bug, for sure. It just merges the two blocks' hardness levels and doesn't account for whether either is actually unbreakable. I'll try to fix it soonish.