SOURCE: Game Boy RND8 There’s something fishy in the GB version of Bubble Bobble: the Bogru team often show laziness when it comes to change the enemy placement when reinventing a specific coin-op stage. They apply strong changes to the blocks layout, but they leave the enemies in exactly the same position. Why? Maybe their late Eighties editing tools were stronger on the block side and weaker on the enemy one? Weird. The best hypothesis is of course that they just wanted to have fun with level design, playing with it and exploiting the immense powers of the Bubble Bobble game elements as a whole. So they kept the enemies in position, then they changed the walls and forced the player to behave in a completely different way.
Check the former GB levels in Lost Cave, or just draw a comparison between AC level 8 and GB level 8. For sure, the dev team loved to add stairways (see also round 2.) Also, the airflows of the revamped round tend to accumulate bubbles in one place instead of splitting them on the opposite sides of the room. More combo chances, then.