Only if the view is that labor must produce profit. Imagine those who write that first novel, paint that first mural, or aid the elderly, because they can financially afford to spend time do those things. A sidewalk chalk artist making everyone's day better with their whimsical takes. Someone at 40, deciding to go back to school as a change in profession, or to gain knowledge for knowledge sake. UBI would only be enough to cover basic necessities, things governments should ensure for everyone anyways. For some people, the basic would be enough.

Labour is not the only thing capitalists need from the workers, they're also at the same time commodity consumers. Even when reaching an advanced level of automation, the capitalists will need people to purchase their products which is where UBI enters the picture. Interestingly, the "UBI" class could actually strike by not consuming stuff.

Anyways i think you're just overthinking, the UBI in the imperial core is only a labour subsidy.