"[Dual] makes relationships with third parties totally dangerous"

[skosh]

One RK Graying in "Information psychoanalysis" (I can't provide any citation) says this in passing about the duality relationship:

"Let me remind you also that the presence of Douala makes relationships with third parties totally dangerous, and therefore mutually enriching."

Could we get some clarification here? Dangerous for whom? The pair or the third party? I found this curious because the implication is regardless of the dual pair (e.g. EII-LSE, IEE-SLI, SEE-ILI, or whatever), its the same result. They somehow are endangered or create danger when a third party is involved. This is especially of interest if a partner in a dual couple is cheating, or when children and other family members are involved. So I was wondering if anyone can provide some insight on this supposedly general rule regarding third parties in relation to dual pairs.