When I booked a long distance bus in Turkiye and in Azerbaijan, the interface showed me the gender of other people, and prevented me to sit next to someone of the opposite gender. There was also a special case for children.
As far as I understand, this is required by law, so Flixbus and other companies had to implement this feature.
As far as I understand, this is required by law, so Flixbus and other companies had to implement this feature.