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HDMI and Analog Audio Connections

An odd note appears in the manual for JVC lcd tv's with HDMI jacks (LT-32X667 and related). The external stereo analog audio output RCA jacks -- for external speaker systems etc. -- are disabled when an audio input, either digital or analog, is present on the HDMI/DVI inputs.
I don't find this mentioned by Sony, Sharp, or Samsung. Apparently only the digital audio output (optical in JVC) is usable -- yet this will also not be operable when analog inputs are used, creating a confusing situation regarding connections to external speaker systems.
Can this be true of other mfgs also but they just don't mention it? A feature of the HDMI interface's copy protection or what not?