Why EAC3 compressed audio instead of uncompressed PCM in Dolby MAT like an Apple TV?

E-ARC has the bandwidth for 32 channel/object uncompressed Atmos no need to do EAC3 compression. This is why Apple TV and Windows use Dolby MAT uncompressed, not lossy and more direct.

You can decode TrueHD to PCM + metadata then just send out in Dolby MAT although would be limited to 44/16bit but then so is EAC3 I believe. True HD can go higher sampling and bit rates over E-ARC since it's compressed and why it's used.

Only reason to use EAC3 is to fit over lower bandwidth ARC instead of EARC, my LG tv will convert/compress Dolby MAT uncompressed from Apple TV to EAC3 DD+ if EARC is disabled and it falls back to ARC due to bandwidth constraints.