It was my suspicion that the change is a result of deliberate human action, but I am not a biologist or a farmer so that's not something I'm certain of. The trend, not the cause of the trend, is what seems more important in this case.

I think everyone misread, including me.

Everyone thought he was saying "are you sure it suggests that? It seems an odd to me because flesh grows over time, so it is a really bizarre conclusion if true!"

But OP didn't mean that. Instead this is what OP meant:

">> The successful seeds were all several centimeters long, 30% larger than modern date seeds, suggesting dates that were significantly larger than modern varieties.

"Actually, maybe it's not that the flesh was larger - but rather, the seed was! The flesh could have remained the same size."

OP then justified why he thought this was just as plausible, by mentioning wild bananas (Google image search "wild banana seed") as an example of large, ugly seeds in a same-sized plant.

i.e. the seeds could have been cultivated to be smaller over time.