This has nothing to do with avoiding "same-sex" issues, since in different-sex animal sexuality the dominace instinct is also operational. That's why its called an instinct...it is always at play.
You want to reduce this to merely physical pleasure. Sure, that's part of it, but its hardly the entire story. Listen, I am not interested in defending or attacking the "gay goose" theory that appears to be the sub-text of the conversation, and perhaps the reason for not wanting to see that other instincts other than sexual attraction are ALSO at play. If that is the ultimate point of the conversation than I will bow out and say no more, as I find the discussion too politically charged and unfruitful. Suffice to say, there are several instinctual responses at play among these two geese in confinement....including dominance, but also automated sexual response to eternal stimuli. Not sure why this is even debated. To remove dominance (or any other instinctual response) from the equation is to turn 200 years of scientific research on its head. This is the basis of all naturalistic and behavioral studies.
As to the dog, YES. The dog is showing dominance over its environment (as well as acting on a clear sexual instinct). There have been many studies on the interplay between dominance and sexuality for canines (especially among wolves). Its not an either/or. Its a both/and. Sexuality among animals is a dominant act. I'm not sure why this is such a controversy. The presence of the dominance instinct does not reduce or negate the reality of the sex instinct.
To the OP, good luck with your geese. Their behavior is very normal and should cause no concern. It does make it difficult to correctly differentiate the goose from the gander at times, which is part of the reason I went with Pilgrims (they are auto-sexing: white = gander, grey = goose).
Sorry, its my dog and I know whats she's doing - I know dominant behavior when I see it, and I know when someone is just set on getting "happy", and thats all she is doing. I know it makes people uncomfortable to think that animals might just be seeking pleasure, but thats been well documented also.