IIRC, yes, it is. If you send audio as analog.
DD TrueHD soundtrack uses higher sampling rate and bit depth than dialog.
When decoding in the player and mixing in other soundtrack (PiP, menu), the TrueHD is downmixed and loses resolution.
To keep the main soundtrack in all its glory avoid mixing any sound into it.
If you bitstream over HDMI, this doesn't happen since no decoding is done in the player and nothing can be mixed together.
Diogen.