I’ve never heard that legend. Troilus doesn’t appear in the Iliad at all, as far as I know, and as far as other legends go, Troilus is usually described as being killed by Achilles in the normal sword/spear through the gut way, either on the field of battle, or when he’s claiming sanctuary in the temple of Apollo.
We studied the *Iliad * in our ancient Greek classes at school. I certainly don’t remember any such incident. Perhaps we had censored versions, but I think a male/male rape might have drawn some comment from the priest who was teaching us. As far as I remember, the references to Troilus in the *Iliad * are pretty scant. I think Priam mentions him towards the end when he’s lamenting the loss of so many of his sons during the war.
All the sources appear to be commentary on the basic texts. Where they are drawing from I don’t know.
Each contradicts the next, of course, so there is not even a consensus death myth to work with. Troilus did die at a result of Achilles’s rape in one version, but because of crushed ribs from a bear hug - a somewhat different image than the one given by the OP.
The OP’s source also gets into the some say, others say game. If you get to cherry pick all the commentaries on all the mythic heroes you can come up with loads of gruesomeness, but you also don’t have to play that game and can come up with very different imagery. Depends what you want to believe and what point you are trying to make, in the end.
In all accounts, Troilus is killed after Hector’s funeral. His death, therefore, does not occur in the Iliad, so that’s why you didn’t read about it in Homer (I can’t remember if Troilus is even mentioned in the Iliad–I’ll have to check on that).
I wasn’t familiar with the rape version that Graves cited. In at least one version of the Trojan War, Troilus was a brave warrior who assumed Hector’s position as the Trojan commander. He is even said to have wounded Achilles before being slain himself.
Richmond Lattimore’s translation of the Iliad, Book 24, lines 253-262 - King Priam is lamenting the death of Hektor, and berating his surviving children:
According to the index, this is the only mention of Troilos in the Iliad.