I don't pay much attention to that number. It would be more useful if the manufacturer would tell me why they chose the number. For example "above x pounds our pack may start to rip apart" or "above x pounds the waist belt may not provide adequate cushioning" etc.

Hiking boots used to be rated for pack loads. I was always skeptical of those numbers too. Twenty years of backpacking in lightweight running shoes pretty well proved to me that those numbers didn't apply to me in any meaningful way.