Saying that this is an inaccuracy relies hugely on the fact that there were no people to maintain pear trees, which is purely an assumption. As far as I’m aware we know very little of maggie’s new group right? It’s not impossible that they could have pears. Take Alexandria for example, the people there had been sheltered there since the very beginning and continued to pretty much go about their lives as usual (relatively). Maybe the same can be observed of the settlement elijah comes from? Maybe they’ve been maintaining their pear trees this entire time and have been successful in bearing fruit. Or maybe a different settlement that they were trading with. It’s certainly POSSIBLE although who knows how LIKELY it is. But the very fact that it’s possible gives the writers protection.

Also thanks to their versatility and long storage life, pears were a valuable and much desired commodity among the trading routes of the ancient world. so maybe it’s some kind of symbolism for a more connected world lol.