I think most bagger goods can get quite wet which makes the contents wet and lumpy. There may be tiny holes where the stitching is or somewhere else on the bag. All it takes is a few holes and the water can seep intot he bag. You can tall by the weight when you pick it up. Also, they get very compressed all stacked up on a pallate.
It's important to remember that humus is basically the final stage and most stable stage of the 'breakdown' of organic matter. Under certain circumstances where humus remains wet it can be almost gelatinous. True humus serves many functions in soil, one being 'aggregation' of soil particles. This is humus serving as a type of glue to bring smaller mineral particle together forming larger 'aggregates' that allow for better water penetration and air circulation in soils. Humus also serves as a sponge for water in soils, so as Gitagal stated, the breather holes in the bag could very well be the reason for the high levels of moisture in the product you purchased and it is the job of humus to hold onto that water. If you'd like to make it easier to incorporate into your soil, empty a bag out on the sidewalk or driveway and let the sun bake it for a day. It will break up nicely and be simple to mix into your soil.