That article fails to actually advance your argument at all.
Firstly, you say, and I agree, that sexuality is a social construct - on the whole it is: most 'sexual' activity is defined by us people as being sexual - the only thing that you could definitely call 'naturally sexy' is the act of reproduction itself: that's the only time that the participant's gender is actually important: so what you should have produced is examples, which do exist, of animals that try to fornicate WITH THE SAME gender.
the examples you gave were simply HUMAN definitions of 'sexual' behaviour as applied to some animals - some of those things (such as 'life-long bond' are nothing to do with the gender of the animal involved) - so you've taken a human definition of sexual behaviour and applied it, meaninglessly, to animals.
In human behaviour we would define bisexual as finding both genders physically attractive - it is meaningless to apply this to dolphins etc, becuase they have no concept of what we call "sexual activity" - that article seemed to think for example that all males groups were necessarily homosexual (football anyone?), or that having a life-long bond with another male was 'sexual'. What rubbish???
Sorry to go on, there was so much wrong with that article it's hard to know where to stop!
Basically the closest thing to 'no sexuality' in humans is not being attracted to ANYONE.
Bisexuality is the next nearest.