PSBT support as defined by BIP174 is an important feature to have for any Bitcoin SDK. It serves as a compatibility layer between different software implementations as well as dedicated hardware devices such as wallets and signers.

One of the superpowers of Swift is the ability to define Domain Specific Languages (DSL) directly over the type system. That presented a great opportunity to have Bitcoin Miniscript implemented as a Swift DSL and have the compiler check its syntax entirely.