The schemas for Amazon and Walmart's product information are absolutely bonkers and constantly missing features that they demand be provided.

Here's the XML Schema Definition for "Product" on Amazon [1]

This is joined on each of the linked category schemas included at the type, of which each has unique properties that ultimately drive the metadata on a particular listing for the SKU. Its wrought with inconsistency, duplicated fields, and oftentimes not up-to-date with required information.

Ultimately, this product catalog information gets provided to Amazon, Walmart, Target, and any other large 3rd party marketplace site as a feed file from a vendor to drive what product they can then list pricing and inventory against (through similar feeds).

You are right that the control McMaster-Carr has on their catalog is the strategic and technological advantage.

[1]: https://images-na.ssl-images-amazon.com/images/G/01/rainier/...

Very interesting how nearly half the list is (assumedly) every single chemical listed under California Prop 65. Do they really need to specify exactly which chemical it is? I've seen thousands of prop 65 warnings in my life but I've literally never seen it tell me what chemical its warning me about. I just commented to a friends a couple weeks ago i wished they'd tell me what so i could look it up myself!