1) CNS has nothing to do with it. Maybe you meant DCS?
2)Getting back in the water to do missed deco stops if you HAVE NO SYMPTOMS seems a reasonable option. IF you have tons of gas and IF you know what you are doing.
1) CNS has everything to do with it. Decompression symptoms in the knee don't cause cognitive problems. Decompression symptoms in the central nervous system include confusion. We know that at least one of the divers has life-threatening CNS symptoms, so this seems quite plausible to me.
Perhaps you were confused by my use of CNS to refer to the central nervous system? It's an occupational hazard that people in my line of work use abbreviations and assume that others know what they mean. In this case, though, I think that the only reasonable interpretation of "CNS" followed by the word "symptoms" is that it refers to the central nervous system.
2) This is somewhat controversial at best. You're referring to making up a missed stop. In the scenario we've been given, of a 300 fsw dive with divers running out of air at depth and only making it to the surface by buddy-breathing, I really truly think the most obvious course of action would be to head straight to a chamber even in the absence of symptoms.