Following the release of the SLEEP corpus during the Interspeech 2019 paralinguistic continuous sleepiness estimation challenge, a paper presented at Interspeech 2020 by Huckvale et al. examined the reasons for the poor performance of the models proposed for this task. They conducted a perceptual experiment on a subset of this corpus that seems to indicate that human hearing is, however, able to estimate sleepiness in this corpus. In this study, we present the results of the Endymion replication study, in which the same samples were rated by thirty French-speaking naive listeners. We then discuss the causes of the differences between the two studies and examine the effect of listener and sample characteristics on annotation performances.