having a hard time recalling modern bikes with a regressive end-stroke. It was popular for a while to compensate for the inherent progressivity of air shocks - to give a more linear coil-like feel.
on the pinkbike chart, the leverage ratio decreases for the first 80mm of travel - this would be a progressive rate. The higher the leverage ratio, the easier it is to compress the spring (think moving the pivot on a see-saw). because the leverage ratio is decreasing, it becomes increasingly difficult to compress the shock as you move through the first 80 mm of travel.
However, from ~85-120mm of travel, the leverage ratio increases. This means that as you progress from 85-120 mm of travel it becomes easier to compress the shock. I’m not a usual fan of this because it will make the bike easier to bottom out on a big hit, like a drop to flat. rock gardens and repeated moderate hits may also bottom it out, but that might be more a function of rebound being a little slow, or needing to finesse the square edged hits. Regardless, it will make bottoming out the bike a little rougher.
It would mean this bike can really only use an air shock (which is unsurprising given the intended use and weight of the bike) with a smaller air can - as air shocks naturally ramp up spring rates (function of providing resistance through decreasing air chamber volume and increasing pressure). Comparatively, coil shocks are linear, the same amount of force is required to compress the coil at the end of its stroke as at the beginning of the stroke. So this frame would make your air shock feel more like a coil - predictably the same feel at any point in the travel
That said, this is all conjecture, maybe this bike is a blast to ride. I Like the coil feel on 150+ travel bikes but for shorter travel I think small air cans work best to keep the frame feeling more playful and responsive.