The question isn't a matter of whether it is useful or works in all cases. The question is whether it is moral based upon first principles. Whether a UBI can feed someone or just amounts to $1 per day in purchasing power, it is a just system.
If people complain about the UBI not feeding people and attempt to morph it into a slavery system where the productive serve the unproductive then society will begin consuming its seed corn. Production will decline and the revised UBI will no longer be sufficient. The process will repeat until money is worthless and there is nothing left to divide.
The system I propose provides a UBI based upon first principles and does so without specifying the purchasing power the UBI would grant.
The biggest danger is people wanting to reinterpret their UBI as something it is not. Once they reinterpret it, then they will either start enslaving their fellow man or denying him his birthright. There is very little room to deviate from the 1 share per person per day without creating a system that is no longer sustainable or fair.