I'm not entirely sure. I'm not aware of anyone dual booting windows 10 mobile. I think dual booting that with android would be a challenge in itself. I'm not entirely sure from the language how windows 10 desktop relates.
It might be possible to adapt a copy of windows 10 on arm, writing your own drivers for windows 10 mobile, android and windows desktop. The mobiles displayed running windows 10 and android are all different, and it's fairly clear the one running windows 10 is a total mess (ie, it doesn't even scale properly to the screen).
Then there's the issue of whether MS or android would allow the licensing, and it's pretty clear they don't like dual boot devices. China used to do a lot of dual boot tablets, by doing a windows and an android version on an intel chipset, and then combining them later after they got the licenses.
However this practice has been entirely stamped out. So even if it's technically possible, it seems fairly likely it's not practically possible.
There are other things that are fairly dodgey about this project as well, such as the low target of only 500 dollars, which is well below the cost of manufacturing a phone, let along the extra cost of drivers and development. The listed company also only has an e-mail, and no social media accounts linked.
If I had to guess, I'd say it's a scam. A company in that situation should at least have a more public profile, and a more demonstratable prototype.