Non-deterministic PEM certificate chain order

https://github.com/intel/SGXDataCenterAttestationPrimitives/blob/c057b236790834cf7e547ebf90da91c53c7ed7f9/QuoteVerification/QVL/Src/AttestationLibrary/src/CertVerification/CertificateChain.cpp#L66-L87

Usually, most PEM certificate chains are defined to go:
- Leaf
- [Intermediate CA]
- Root CA

Even most of the [sample files of the attestation app](https://github.com/intel/SGXDataCenterAttestationPrimitives/tree/master/QuoteVerification/QVL/Src/AttestationApp/sampleData) use the same order, with a few exceptions.

My question here is, why is the order indeterministic in the first place? As you can see from the code example above, it makes parsing more annoying.

Can I expect the Trusted Services API to always return a proper chain from Leaf -> Intermediate -> Root CA? Or is the order really "dunno, you need to check"?

And if it really is designed to be non-deterministic, why is that?