Netflix uses DD+ and there's no DD core in it, but an official Dolby decoder

In short DD+ = core + extension
Dolby site states: Dolby Digital Plus, by contrast, uses a “core plus extension” structure, a new and unique technique to address downmix compatibility. The core is a complete 5.1-channel mix, while an extension contains any additional channels.

EASC3 to AC3 official paper says:
The amount of decoding and encoding required during the conversion process depends on how the E-AC-3 frame is encoded.

That means: You can just cut "core" and send via SPDIF , encoder/decoder is needed -> issues can happen

Tested a lot of movies and apps in the past and know how many issues apps had with different audio codes ..

still dont know how good is Netflix in this =)