The highly liquid index futures exhibit seasonal trends like the cash indices. They vary from country to country even though similarities in seasonal cycles exist.
Index spot and futures prices vary as well. The difference between spot and futures prices results from the interest and dividend payments which flow into the arbitrage relationship
Indeed it may be small, nevertheless differences exist. For that reason charts under the "Futures" heading should be used for analyzing futures only. For trading in the futures market, the seasonality of the futures market is definitive.