So I moved my money out of the account. That worked fine.
But for the other 99.99% of signatures in the world, any mark at all is fine, and insisting on more is wasteful bureaucracy.
"However, many jurisdictions still require a wet signature. For instance, in the US and Canada, notarized documents require signatures in wet ink. Similarly, documents in areas such as family law, wills, trusts, or banking also require physical signatures. In the UK, tax authorities require a wet signature for any tax documents filed by a British resident."
https://www.adobe.com/acrobat/business/resources/wet-signatu...
Without diving into too much minutiae, a legal signature can be any mark the signer intends to act as a signature. It could be a bird you've trained to poo on command onto signature lines.
In my case, this instance with Schwab was the first of a lot of similar paperwork I was going to have to do, so I pulled the ripcord when I saw how they were going to approach it.