In the normal job selection process, first a job is created and then the matching system looks for people to match to that job. Once you get to the margins you end up with jobs that cannot be filled and people that cannot get jobs.
You have a matching problem.
That can only be resolved a little bit via training, job redesign, sanctions, etc. and you always end up with a list of vacancies and a list of people who want a job.
The job guarantee is different.
You take the person as they are and you find/build a job for them as they are.
You are guaranteeing a match because you are helping the person to become employed as a function of the programme. Coming up with jobs is part of the process.
Think of a bespoke suit made specifically to fit from a selection of templates, rather than trying to squeeze into an off the peg affair.
The result is that the list of people who want a job becomes empty. That is the key difference that makes a Job Guarantee a Job Guarantee.
Standard employment, workfare schemes, and even normal public sector employment can only provide people for the jobs.
It takes a Job Guarantee to provide Jobs for the People.