First, I assume you mean a Blu-ray Disc, not a DVD, as DVDs don't contain HD audio such as TrueHD. Second, yes, the PS3 is decoding the HD audio from the disc and sending it out as PCM multi-channel audio to your Denon.
The Denon is properly letting you know that it is receiving multi-channel audio as decoded by the PS3.
You are good to go.