Random use of the plural. So annoying. Be consistent duolingo. What do native speakers actually say?
We're context based, you say "Pekerja-pekerja itu pulang." when you wish to be clear that more than 1 workers (but you don't know if all do), is going home.
Native speaker say:
Pekerja-pekerja itu pulang
Para pekerja itu pulang (para equivalent to all or many)