G6 Lens Hood Question

Just bought yesterday lens hood LH-DC30 for my beloved G6 (new gift for him and I have a question about it. Manual says: " When using the lens hood, you cannot attach any other optical accessories to the camera" but why adapter which goes together with lens hood has threads? (but kind of wider threads).
It means that with lens hood I could not use any filters for example?
Any opinion about it?
)good that lens cap, original one, suits to that adapter, which goes together with lens hood).
This is a picture of the threads:

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I think I understand now , apparently Micro Ring Lite fits to that threads:
http://www.dpreview.co​m …s/Accessories/m​r-14ex.jpg

I don't have the LH-DC30, but from the picture, I would say those are not threads, merely ribs for strength/appearance, possibly they even help cut down on direct reflection of light from smooth plastic.
I think the macro flash is an entirely seperate piece--it's just the mounting looks similar.

Generally, you wouldn't want to mount anything on top of a lens hood, because the hood would no longer be shading that component from stray light. Despite the doc, you probably could mount a filter to the lens tube, and then mount the hood to the filter--the only risk is vignetting at wide angle zoom.
Some collapsible rubber lens hoods are threaded on both sides, because the hood extends far past the intererior thread. I've found I can stack mine (from lensmateonline.com) between two filters without vignetting, and still get reasonable shading of the top filter.

I have my lens hood on all the time. But I found it irritating that I had to buy another adapter if I want to use filters.

Yes, and you cannot use lens hood with another adapter, which you use with filters. This is strange engeneering decision Canon made.