Any non-unionized employee paid less than 3x minimum wage is considered a contract employee and has a minimum wage of ~2x federal minimum wage. (possibly an addition about % contract employees allowed)The first part deals with professionals and other higher paid workers who are less likely to need union protection. The other part does a few things. On the surface it discourages union membership by putting a higher salary floor for non-union workers, but it also makes them "contract" employees which changes lots of the other benefit structuring around. It's actually still a pretty good deal for younger workers who aren't working as a career yet (college students) but for older workers, those with families, and those who see this job as a start point for their career, that higher pay isn't as good a deal as lower pay with benefits, more job security and union negotiating that will likely mean better pay down the road.
For employers, the ability to hire at a lower salary will help make unions more palatable, and the ability to pick up contract workers for seasonal jobs will allow for flexibility.
So basically employeers have 3 options: pay employees at least 3x minimum wage, encourage unions and hire union workers, or hire "contract employees".
This idea comes from this string of thoughts: wages have stagnated, but the minimum wage is a clunky tool to fix it (hurts smaller employers in less costly parts of the country, maybe doesn't do enough in NYC, San Fran...). Additionally unions have shrunk to almost nothing and, most notably, as the employment profile of this country has shifted from manufacturing to service, it is service workers that are, broadly, not unionized. There's no good reason for this, entry level manufacturing jobs 50 years ago were in fact not skilled positions, and the qualifications for those jobs was no more than the qualifications to work at a mall store, fast food restaurant and maybe lower qualifications required than some service positions (home care, university lecturer...). Unionization would be a far more versatile way to address working wages and conditions.
The problem is that currently, the push is strongly against unions, and so we need a way to push back against that. It needs to be structured in such a way that employers are less likely to fight against the formation and expansion of unions. Making it possible to pay entry level union workers less sounds problematic for unions, but if those are the jobs avialable (and if you can be easily canned from a contractor position if someone does come in with the union) then they may not really seem to be the worse option. Also, if yo have to pay full social security & medicare from your paycheck and aren't getting any paid time off and don't get to set your own hours and don't get any raises, then you may see that lower starting paycheck as not too bad a thing.