Why then tie it to labor at all, why not the full UBI? Also why tax credits - many low wage jobs aren't well served by annualized refunds (you can see that in stats where medical visits surge for a bit after tax refunds...).
A UBI of course has a lot of other benefits (being distributed monthly or more often, going to people who are unable to work, being universal and therefore more resistant politically).
You’re right that annualized refunds are far from ideal. Monthly would be better.
Argument in video form, with diagram below.
https://mru.org/courses/principles-economics-microeconomics/...
Also, tax credits can be (and are) paid weekly.