The published numbers are minimums. Having a lower minimum doesn't guarantee that they will take anyone with that experience, it just gives the recruiters more options.
When you get a hiring boom many of the operators are all competing from the same talent pool, so the more experienced troops get soaked up quickly, if they set the minimums at the level they expect to hire at, then there is no room to move. If they set a lower minimum (but still at a point that they can manage from a training perspective) then they can look at the demographic of the new hires and perhaps mix them up so you have a combination of experienced and less experienced people, who will have different expectations in relation to command, type changes and base transfers etc (potentially will retire at different points as well).
Single pilot ifr ops are the hardest thing you will ever do. Regional flying isn't as hard in many ways, but harder in others - a much greater reliance on the crew, throwing bags, trim sheets, briefing/feeding/managing the punters, multiple sectors into uncontrolled ports/ctafs etc. lower pay than the airlines for harder (in my opinion) work.
In many ways I would funnel the more experienced people into the regional style operations and the less experienced ones into the jet, but that isn't what the prospective new hire wants, for valid and reasonable reasons.
If I could figure out a way of paying regional pilots more it would be good but unlikely given the way the market for pilots works.