My understanding is that the stock Logic Pro X instruments are not standard VST plug-ins, rather they are AAX plugins which will not work in Studio One. Because you cannot insert the stock Logic Pro X AAX instruments into Studio One, you cannot access the presets. The presets alone are designed for the stock Logic Pro X instruments and are meaningless to any of the stock Studio One instruments. So, unless Apple also provides VST versions of the stock Logic Pro X instruments that are compatible with Studio One, you are not going to be able to use those presets in Studio One.
That said, you could always create tracks in Logic Pro X using those presets, then bounce those tracks to audio, create stems, and then import the stems into Studio One.
