The issue with all the 2/3+ hybrid multisig companies is that they have the xpubs, and have to, otherwise recovery is impossible unless you lost a key but not that key's xpub. This solution is just more bespoke. Admittedly cool. You have to accept the trade-offs. For some people's situation (business, family, living arrangement) it makes quite a bit of sense, just not for mine or DIYers.