Actually, I tend to agree with the assessment in the article, namely, that Jesus was referring to only the last part of the prophecy and that's the generation he was talking about - the one that sees 'the sign of the Son of Man' appear in heaven as related in verses 29-31.
In fact, I think the Society should have (and possibly still will in the future) applied 'this generation' to the generation that witnesses and lives during the Great Tribulation.