Hmmm pretty sure Yoshida clearly stated that burning garuda down before she could Aerial Blast was because of a mechanic of the fight not working as intended.
It might have been an oversight by the developers and yes they quite clearly said they wouldn't punish people for the exploit, but they stated it wasn't the intended way to do the fight and yet people still abused it even after they were told it wasn't intended.Director/Producer Yoshida here.
In regards to the video, this is occurring due to the fact that the remaining HP percentage check is not being processed at the time of Garuda’s AI phase change. We are currently looking into fixing this.
So either you yourself do not understand your own meaning of the word exploit or you basically just contradicted yourself.
The developers basically decide what is an exploit and what isn't, if its not the intended way to do something and is against the rules they will fix it, which surprisingly enough is exactly what happened to the garuda exploit.