Some may be application notes from the manufacturers.

Jameco also supplies mid level engineering firms, so similar to application notes. Think automation integration company buying xyz specialty robotics controller.

I think of mouser as more like digikey, so I don't really know why they would have similar educational information above the level of PCB board component. But, they may also have business in the low-quantity higher margin business.

Tldr: not seo. Customers actually need to know about the product

Exactly, as one of their target audience I'm not searching for them, I know who they are. I go to their website regularly and articles like these are how I find out about new stuff and how to use it.