He’s separating attraction from action, and saying that being attracted to same sex is far different from having sex with the same sex.
Just as a man might be attracted to a woman who is not his wife, but that isn’t a sin. The sin is when he acts on that attraction, and has sex with a woman who is not his wife.
Similarly, one might also be tempted to steal, lie, cheat, or even kill,but not take the step to act on that.
OK, so, to paraphrase some other sin into his quote -
“it’s not a sin to be tempted to steal something, but it MIGHT BE a sin to actually steal it. MIGHT BE.”
What he’s saying is that it MIGHT BE a sin, which means he’s saying that it possibly could NOT be a sin.
If he were, as you say, separating the act from the temptation, he wouldn’t have said “might be”, much less RE stated “might be” for emphasis.
Read Matthew 5. Jesus says that if a man looks at a woman with lust,he has already committed adultery, and the same with murder. Thank God for His grace and forgiveness!