So I habe recently stumbled across a subreddit about people not getting that people are homosexual, and actively searching excuses why that can’t be. A lot of posts in there were about historical figures, like Achilles and Patroklos, being classified as straight or just having „intimate relations“ by historians. Is that an actual existing problem?
It sounds like you're talking about /r/SapphoAndHerFriend, which focuses on LGBTQ+ erasure in and out of academia. This erasure often seems pretty blatant—a woman writing sensual, erotic love poems addressed to another woman is almost definitely lesbian or bi, right?—so when people see these poems and think "Wow, they must have been really close platonic friends" instead of thinking "That woman isn't heterosexual", it can be, to say the least, frustrating and invalidating. LGBTQ+ people have been left out of a lot of history, and this lack of representation gets used by people to deny their existence; if they were there the whole time, and the straight/cis historians telling history have been mis-portraying them as not queer, then that's all the more a problem.
While that kind of erasure does happen, these posts do overlook a problem with discussing sexuality: different cultures in different regions at different points in history have had very different understandings and perceptions of sexuality and sexual identity. The concepts of identifying as "heterosexual" or "homosexual", for example, are relatively recent ideas, even if the acts of heterosexual vs homosexual relations have been understood for millennia. And so using modern-day language based on modern-day concepts to describe non-modern people who didn't have those concepts creates challenges for academics to engage in the topic properly. Sometimes this does take the form of queer erasure—there are definitely people, especially early scholars, who refuse to perceive certain historical figures through a homoerotic lens—while sometimes it just looks like it but is really them trying to adequately sift through all the personal and cultural nuances of the situation; it's not so much about misrepresenting queer people in history, but rather, trying to avoid anachronisms when representing them.
Now what I just wrote is really just a preamble and not an answer (this is not my area of specialty, and apologies if I've butchered anything here). More can be said about how academics engage with LGBTQ+ representation in history, so if anyone has something to add please chime in! But in the meantime you may find these older answers helpful in really addressing the issue at hand: