I'd expect nothing less from them. The right thing to do here is to implement a sorting key for different categories here. Since McMaster-Carr seems to be going to a category when you search, they seem to have better control over the available filters.

I've found that on a site like Amazon or Walmart that'll let you do a more freeform sort, the filter options becomes absolutely god awful.

Well done by McMaster-Carr. I assume they control their inventory a bit more than a marketplace like Home Depot, Walmart, or Amazon, so that's also an advantage.

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/...