So he "researched" and found a limitation of MW known since 2016. That's $60 well wasted.
https://github.com/mimblewimble/grin/wiki/Grin-and-MimbleWimble-vs-ZCashWhile Grin transaction outputs are fully obscured, it's still possible to trace which inputs links to which outputs at least until some age. But it's unclear at this point what information could be derived from this.
Also,
https://github.com/mimblewimble/docs/wiki/Grin-Privacy-PrimerInputs and Outputs Linking
Transaction aggregation provides benefits, and the absence of useful information in either inputs or outputs complicates analysis drastically. However, there are techniques that can exploit linking between inputs and outputs to erode privacy guarantees. Practically, they all need to rely on having participated in a transaction "close to" the ones that need to be analyzed in order to gain additional information. By sending "tainted" outputs and following as they move through multiple transactions, information can still leak as these outputs can be followed after one hop, or statistically over multiple hops.
This is an area where more improvements from the Grin team can be expected in the future, after mainnet is released.