The more I think about it, I am just thinking that Spark has some API endpoints that do cool stuff with Bitcoin. It's not decentralized, the "self-custody" thing is sort of like a legal detail -- it's not real self-custody, because in the end you need to use their API to do anything -- but -- otherwise what spark is offering is not massively different from APIs offered by other companies, or that you can roll yourself with LND or CLN or LnBits or even BTCPay server, if you like messing with Linux. And now that I think about it that way, it doesn't bother me hugely. It's just that people need to know what it is. I guess I was taken in by the marketing and had higher expectations than were warranted.