No, those 63 are all of the plants from the base game and expansions. It might be worth trying the different emotional charges on crystal flowers, to see whether it makes a difference (although you'd be more than 2% short if that was the explanation).
The game does seem to get its percentages muddled quite often. I've certainly had Sims who've caught more than 100% of available fish. It usually seems to happen when playing without some of the expansions, which obviously isn't the case here. There are another 13 plants in store content, though (Bohemian Nuts and Fruit, Humble Harvest Stands, Grandpa's Grove and Grandma's Canning Station) and I wonder whether that's confusing the score.
