I've had Pumpkin seeds stock a couple times in the mole market, but they only stock 5 at a time, and they require 3 seeds per planting. I don't think this is intentional since most other seeds stock in amounts for more plantings at once.
If I counted and remember correctly, all the old seeds always stock in quantities equal to 4 * the amount required to plant them. So it definitely feels odd that this one only stocks 5.