I say unusual in the sense of Japan seems to be the only one to have solved the issue of how do you transport 2 kids on a bike not with "big box" like the dutch and subsequently the entire western world but via 2 seats, they're apparently very popular over there as a means of transportation.
Rear facing seats support a baby's and toddler's head and neck in the event of a head on collision - as opposed to front facing where little little kids heads will rock forwards (they have big heads and not well developed neck muscles to not snap forward). So, not likely or whatever as a cyclist lol. I guess it'd be more likely if some wacko motorist hits a cyclist at low enough speed itll support the baby at the front to be safer.
It's not exactly fun for the kid to have to face their parent instead of the world, but it's safer I'm assuming. But maybe the designers did the safety engineering already and figured it didn't matter I dunno.