Nothing I said had anything at all to do with thinking or treating anyone as a "surrogate", nor was it an occasion for a "ooh yowch". What I said was that if my partner of 15 years had another boyfriend and spent a great deal of time with him, I'd have to fill some of the time that I've been spending with him, and doing so (under such circumstances) would likely go smoother for me if I also had another boyfriend.
The underlying question had to do with the distinction between jealousy, per se, and insecurity. As I said, I don't find myself particularly prone to jealousy, but that some kind of insecurity might arise. That's called being honest. It's not called waiting for the Real Mr. Right to show up whilst I treat my partner as a "surrogate" for Mr. Right.