Basically, if you want two people to watch/listen to media on one phone with headphones, you either have to share one set of headphones with one ear bud for each person, or have a headphone jack Y splitter to plug in two separate headphones.
For existing (firmware update?) and future Huawei phones with a 3.5mm headphone jack AND a USB C port for headphones use (eg: Mate 20 regular) Huawei can "enable" sound to pass through BOTH headphone ports at the SAME time. Something not currently possible on any smartphone I believe. A first for Huawei.
What do you think? Useful? No extra splitters needed.