I agree with you, but for different reasons.

The first three letters of "LGB" are inclusive because most people who aren't part of the heterosexual majority are attracted to either people of the same sex or to people of both sexes. Because sex is distinct from gender & gender identity, this part of the acronym is inclusive.

Then there is the "T" -- which also includes transgender people who aren't part of the cisgender majority. A lot of people tend to forget (or not realize) that trans people can be heterosexual, homosexual, or bisexual -- but they don't have the privilege of being assigned to a body corresponding with their gender identity from birth.

Now, obviously, there are other gender identities such as nonbinary, genderqueer, genderfluid, genderflux, nonconforming, agender, bigender, etc. These categories are all very diverse, so the "Q" for queer (as a fifth letter of the acronym) covers them.

People who are pansexual or omnisexual have even broader levels of attraction than people who identify simply as bisexual; however, "pan-" and "omni-" essentially fall under the bisexual umbrella, even though there are variables that distinguish them.

So LGBT+ or LGBTQ+ should be sufficient, for the sake of brevity.