> describes both the incentives to not do that

It's a bogus claim (as I previously stated). Applying the same technique in another domain or for a different purpose does not defeat the original purpose for which a technique was developed. People can do both things.

No one said anything about printers using synthid. The modernized variant (at least one of them) would apply to digital media produced by the end user.

Although since you asked, if the synthid watermarking scheme is more resilient to transformations and conversions than the current one then switching might prove useful.