This made good sense to me:

Most of the people who would benefit from privacy-heuristic feedback are the people least equipped to run it safely. They don’t run a node, so the path of least resistance is to paste an xpub into someone else’s website.

It sounds like he's using bloom filters with some extra fancy cryptography stuff to make it so that the server cannot tell which outputs you are querying for.

This thing jogged something in my memory and I thought I may have posted about it before, but apparently not. But it is part of a product he is designing called BTC Medusa:

this is the cryptographic core of a product, a fork of Sparrow Wallet with a paid token model where tokens are sold in packs and payment is what gates blind-sign issuance is what I have built.

And perhaps like whirlpool/wasabi, it may point to a revenue stream for open source wallets (although, I'm not convinced that it is very big):

Also, I’ve laid out in my whitepaper explicit mechanisms to implement revenue sharing with open-source wallets that implement this protocol since revenue is the most difficult part for open source wallets to maintain.

Here is an example of how their are pricing it at the moment (in his delving post he mentions tokens, and this seems to be a price to download the plugin, so maybe there is also an additional charge for use):

Run own UXTO is not for beginners.