As a queer person, these are people I've met in my lifetime:

Females loving other females, both naturally born as female

Men loving other men, both naturally born as male

Females born as female loving people born as female but dressing as a male

Men born as male loving people born as females who dress as men

Females born as male (transgender) loving women born as female

Lesbians who have sex with gay men

Men born as female loving men surgically turned into women

Straight woman loving a straight man who likes to dress in women's clothing

A phenomenon known as "stone butch dyke", generally regarded as male-like, primarily into femme lesbians

People who identify as androgynous, hanging out with drag queens, who can hang out with transgender people, who can hang out with lesbians, who can hang out with gay men

Bisexual and polyamorous people of all of the above flavors loving all of the above flavors

Women with bodies that don't feel right and they don't have surgery but identify as male because it makes more sense, and they can partner with straight women, straight men, lesbians, other women whose bodies feel more male

Hermaphrodites who really are on the fringe, more so than transgender

Androgynous asexual people into theatrical drag and bottom for gay men or women dressed as gay men, or women surgically turned into men...

and so forth.

So, can't tell you objectively if transgender should be included in LGB, but personally, it makes complete sense to me.