I used to feel that way myself (though perhaps with a more Type 7 take on the matter) but I don't so much anymore. When Lil described the way she as a Type 4 would choose to pursue a man, my immediate thought was "that is exactly what my H would want". My fantasy mate Hank is a Type 7 like me only better. So maybe everyone's ideal soulmate is just a mirror-image of themselves but higher functioning. But in real life, matings of like-types doesn't always work that way. For instance, although I think what Lil says she wants to offer a man is just what my H would want, I think they would last approximately 13.5 days in a relationship together, at best. Also, when Lil described her Type 7 BF as someone who "always has a pie on hand" this was immediately appealing to me but on second thought I realized that I wouldn't necessarily want to be in a relationship with a man who "always has a pie on hand" because that is the role I see myself filling in a relationship. We might end up with a mean-spirited pie-bake-off competitive type relationship. So, I think everyone has a fantasy alternate mate but that this is to some extent a narcissistic fantasy along the lines of "I am so great. Why can't I be with somebody just like me so they would appreciate my greatness.". If you fear the fact that your partner may be having fantasies along this line it is probably a reflection of your fear that you may have gone too far in reducing validation in the relationship without adding value. Therefore, you can reduce your uncomfortable feelings by either backtracking and validating your partner or by adding value. For example, if you went out of your way to buy your H a set of Star Trek DVDs and said "I bought them for you because I really appreciate you as a husband." you would greatly reduce your fears that he doesn't see you as a soulmate. However, I don't know if reducing your fear in this manner is what will aid your relationship in the long run.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver