Is Lephantis Working Correctly?

[NinjaZeku]

Just did the Sortie Lephantis (Elemental Enhancement, oh yay a more sponge-y bullet sponge lol), solo (because I felt like it),
and while I didn't run into any gamebreaking bugs, I do have to pose a question as per the title, let me explain:

As the fight went on, heads appeared to spawn faster, until most of the time, all 3 heads were active at once,
and they did seemingly random anywhere from 0 to 2 attacks before diving down again.

Now, the first time I fought this boss was quite a long while ago, but I'm pretty sure I remember correctly
when I say that, back then (and for a good while after), heads popped up 1 at a time, and always did exactly 2 attacks.

So, what explains what I witnessed today? Was the fight intentionally changed? Maybe for Sortie only?
Or is this indeed Bugframe at work? I just can't tell at this point, so an official reply would be great, thanks in Gameboy Advance.