Jez, what you may have not noticed and what could have been what you heard was ..... After the guy dropped the pitch he then incrementally dropped the speed as well. That could have been the warbling you heard as it dropped step by step in speed.
Personally, I do not foresee it as necessarily being a flaw of some kind. Of course we'll know more down the road.

Wait, after listening again, I see what you mean. I agree something sounds amiss. Sigh