I hear the (normally silent) "ent" of the ils/elles conjugation. I wondered if I am hearing things: I'm not crazy! https://blogs.transparent.com/french/french-interrogatives-inversion/ "...There can be some changes to pronunciation with inversion... [We know we] don’t normally pronounce the ending of third person plural verbs (like (ils/elles) dorment or disent). However, in their inverted form these endings must be pronounced. Thus, if you are asking if a group of people are sleeping:dorment-ils? You would actually pronounce this dorment-Tils?" However the difference is very small.