I was talking about the opposite--the inability of an sRGB monitor to accurately display Adobe RGB images. And sRGB is very much a smaller subset. It fits entirely within Adobe RGB.
Maybe someday PhotoPro will be practical to work in, but not today as far as I'm concerned. There are still few monitors and no printers that can do justice to even Adobe RGB. And my Nikon D800E only captures a 14-bit color depth anyway. Until I'm dealing with 16-bit sources, ProPhoto doesn't really buy me anything I can use. And if someday I do begin to work in that color space, I'll still have all my old RAW files I can apply it to if I want.
1. sRGB being a smaller gamut than Adobe98 is a given. However, most sRGB monitors don't limit a sRGB image to only a sRGB gamut. This is where the NEC Spectraview II monitors are great imo, they 'clamp down' the sRGB gamut when in sRGB mode so all you're seeing are colors/levels n the sRGB gamut. The correct subset. Otherwise depending on the source (camera, scan, etc) and the actual limits of the video card/profile.. even when all is set to sRGB.. colors outside the sRGB gamut can create casts. You might make 1000 captures and find (depending on the scene, WB, and exposure) 300 have a red cast outside sRGB, 200 green, etc, etc.. It's unpredictable.
2. Adobe strongly recommends using ProPhoto and in fact have made it the LR default. They probably have a good reason. I personally find ProPhoto's gamut more centered and consistent across the board. To me it's worth it just to stay consistent to LR and it's not causing any disadvantages I can see..