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 12:1. The disciples were stealing food, at least in our context, but the issue The Lord addressed isn’t whether it was wrong to take food that didn’t belong to you, but the argument was about doing it on the Sabbath.