On the CoC API, I found something interesting. I placed my Player Tag to generate the stats of my profile, including the achievements and troops as well. But the order seems different for both. It seems that they are ppaced in chronological order, so most likely when they were placed in the game.

On the Builder Base troops, their order was by far more messed up than the other orders, so they current order of the BB troops was not final

The first 2 were RB and SA, nothing strange so far. The 3rd one was actually the Beta Minion and the 4th was the Boxer Giant. It seems that the order of those troops were swapped during development. The 5th one was the Bomber, not strange at all. Then the 6th one was the Super PEKKA. Really mind blowing. It seems that she was unlocked earlier in the game, perhaps at BH5 which could have been the last BH Level. But she would be really overpowered if she was available from BH5, glad they moved her to BH8.

Next we have Cannon Carts. They must have been placed in BH5, while SP would move to BH6. She would still be overpowered there, so the next troop came to BH6, which is the Drop Ship, while SP moved to BH7. Really smart move from Supercell to release the Cannon Cart and Drop Ship, otherwise Super PEKKA would run rampant in the mid BH Levels.

Thr last 2 troops were the Baby Dragons and the Night Witches. By what has been shown from above, it seemed that those 2 troops were not supposed to be released at all and they might have released them to fill some spots for troops. Perhaps they could not find an idea to add in their place, so they were added instead.