The idea behind Basic Income is to remove government intervention in the economy. Coupled with a flat tax, it massively reduces government overhead and bureaucracy, and leaves government to it's main role as the arbiter of society.
Governments' main role is to enforce the rules a society is based upon via the social contract. Collect taxes, enforce laws, and invest in the unprofitable but necessary foundations of civilization (infrastructure, healthcare, research, conservation, etc.)
In societies, as in design, less is often more. The more lifelong government bureaucrats we create, the more perverse incentives exist for them to parasitize the government for their own gains.
So why do we need to legislate for minimum work hours if we have a sufficient BI? And in what fictional universe does open borders make sense?
Human beings are competitive, and we form tribes to compete against one another. This is healthy, and leads to great achievements when properly channeled. The Cold War, for example, caused an era of unprecedented technological innovation. As we enter the post-war era, we already see the downfalls of globalization. When there is no need to compete, decadence sets in. The rich hoard money, and governments refuse to invest in their people's future in the form of infrastructure, research, etc.
We need borders, and we need a competitive immigration system that behaves like a sports team manager who is constantly on the lookout to poach talented individuals from competitors.
Competition is the quintessential human trait which has brought us to where we are today. Setting it aside has always lead to decadence and downfall.