Hey Vigarus can i be very warm and tactile with you? heheheheh
Yeah so I think this is a bit of a loaded question that could maybe do with some breaking down.
Because the word gay is an inaccurate word so is the word gaydar. The mindset of any gay or bisexual identifying person toward their own sexuality is always an extremely complex thing. As with heterosexual men and women.
So if sexual identity is an amalgamation of psychology and biology then gaydar must be the same.
So on the psycology side of thing you could say gaydar is a complex ability to read subtle body language and key social signals people give to indicate they are sexually available to that person, on a biological side as the article the poster has linked
Solving the Mystery of Gaydar | Psychology Today indicates that there is also a chemical componant to "gaydar"
Both of these explain why many str8 men claim not to have gaydar on the psycological side of things reading the minutia of body language requires a strong sense of intution and sensativity two traits that were untill recently discourages in men
and on the chemical side of things of the brain is not familiar with recieving this particular chemical signal then it would go unnoticed in much the same way as humans dont recognise the chemical signals of bees or ants