Do you see SIPER test missile "the Booster" is small one as length size compare to Aster 30 missile.
For me it means that they can put large one to increase range, my be later or if it is need it.
Maybe because it doesn't need such a large booster. If HISAR-O+ can reach 50km without a booster, then Siper can surely reach 100km - especially considering the fact that our missiles are equipped with dual-pulse rocket motors whilst Aster missiles do not.