The explanation would go something like this (I think, but I'm not a proponent of the system):

You'd give them the same payment, but you'd take back a much higher payment in taxes. Giving people $40k just to send a bill of $100k seems inefficient to me.

It's just an accounting movement, you don't need to actually transfer them the money so that they can pay it back. You calculate their balance and just tell them to pay $60k.

I support Universal Basic Income. In my opinion, the main problem a UBI would tackle is non-participation. We can get more people to take benefits if we show that everyone takes the benefits.

Of course, other supporters will talk about the savings with decreased bureaucracy costs but those are like nice bonuses to me. Personally, I want everyone who is eligible for a program to enroll and benefit. Yes, this could mean increased taxes but I think it will be well worth it.

UBI is often described as a negative income tax for a reason. You don't send those people the money, you give them a tax credit for the money.