I don't know but if I remember it correctly Green Wallet lets you store a single seed phrase that's you secret. They keep the other secret making it a multisig.

"Although Blockstream Green uses industry standards for recovery phrase generation, wallets created in Blockstream Green using Multisig Shield cannot be restored on other wallet software. This is due to the unique multisig security model used for Multisig Shield wallets. In comparison, wallets that use Singlesig can be restored on most other wallet software (e.g. Electrum).

In order to restore BIP39 wallets created on other wallet software, you can select Migrate Another Wallet when restoring a wallet on Blockstream Green."

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1. AQUA SERVICES

The AQUA Services enable you to create one or more single-signature, hierarchical deterministic (HD), non-custodial cryptocurrency wallets for certain supported digital assets, known as the AQUA wallet (“Wallet”) and to use the Wallet to store, send, request and receive supported digital assets.

Our Services are intended for use by persons who are knowledgeable about cryptocurrency generally and HD non-custodial wallets in particular. If you use our Services, you represent that you qualify as such a person.

Subject to the Agreement, we grant you a limited license to reproduce portions of AQUA Content solely as required to use the Services for your personal or internal business purposes. Unless otherwise specified in a separate license, your right to use any content and service is subject to these Terms. We are not a bank or financial institution and do not provide investment or financial advice, or consulting services to users of the Services. AQUA is solely the provider of the Services.

You must provide all equipment and software necessary to connect to use the Services. You are solely responsible for any fees, including Internet connection or mobile fees, that you incur when accessing or using the Services.

Etc pp

https://aquawallet.io/terms/

Might just be unfortunate wording, I'm interested to learn what they say

Me too!