To my (UK) ears, normal audio pronounces coś as cóś. Slow audio is OK. (Female audio in both cases.)
I've heard cóś in other exercises, too.
EDIT [(~3 weeks later) 10 Feb 2019 08:40 UTC] All my exercises over the past few weeks used only the female voice. But whenever the Discuss page has (normal-speed) audio, it's always the generally far better-enunciated male voice – maybe 'he''s 'her' younger brother, better trained in TTS?
At the top of this page 'he' clearly says coś – but I unexpectedly hear no trace of w...