In this case, though, they did identify as gay: "But Syrett writes that the 50 letter-writers he studied identified as gay, at least privately, and did not marry women. "
Note, I do agree with you, I am trying to clarify terms only.
I'll also note that a lot of gay people from that era report that they felt pressured to be heterosexually married to fit in. I have a couple of friends from a more recent era, currently in their mid 60s, who felt that pressure when they were younger. One had "an arrangement" with his wife, and two "came out" in their 50's and had extremely messy divorces.