The meaning of the viewing always refers to events in the future, the images/symbols present in a viewing are not necessarily from the future - most of them aren't. They can be from the past, present, future or be completely "neutral", symbols, and even colours. The Towers in ruins are an event from the past. That they appeared in a viewing means they represent something relevant to Lan's future, that's all.

There's no good reason to conclude from RJ's explanation the images used in the viewing of Lan aren't of Lan himself as a baby, as most likely they are (Min so far seems to always know when a baby in a viewing means a future actual baby for the mother she viewed). These images combined would be a symbol of his oaths to lead the Malkieri survivors to avenge Malkier (represented by the Towers in ruins) or die trying if necessary, an oath that was taken for him by his parents over his craddle.. before they went and died trying (thus the image of Lan as a baby. The key to understand this part Jordan put at the end of EOTW.. and revealed at the same time that Lan refused to raise the Golden Crane. With KOD, the viewing is no longer mysterious, IMHO). It's a "private war" Moiraine had convinced Lan to put aside to join her cause, but Nynaeve made him return to it, and made sure he wouldn't interpret the oath as he wanted, by leading a meaningless suicidal solo charge against the Shadow, refusing to lead the Malkieri or other men. That viewing would have referred to the future, as it would indicate that down the line Lan would raise the Golden Crane and lead the Malkieri to war against the Shadow that destroyed the nation, fulfilling his oath as the Malkieri heir. This has started to happen in KOD.