In the 1960s and 1970s, there was a more restrictive and limited vocabulary around what would become the LGBTQ+ community. Case in point: most of the words represented by the letters in the acronym were not in common usage or had different meanings at the time. A further example: Bi people were mostly not acknowledged at the time. If someone were attracted to someone of the same sex — whether also attracted to the opposite sex or not — they were called gay or, more commonly, homosexual.
When Sylvia first came out, the only words she knew to describe herself were gay and a transvestite. You acknowledge that what she called herself changed with time. Couldn’t that be because she finally had the right words to describe herself?
I know someone who thought they were gay because they were attracted to the same gender. Later they realized they were attracted to genders other than their own and identified as Bi. Saying Sylvia wasn’t trans because she once identified otherwise is like saying this person wasn’t Bi because they once identified as gay.