It seems like you're right and they're different; there are apparently a whole bunch of different species. Sansho is Zanthoxylum piperitum and green sichuan pe

It seems like you're right and they're different; there are apparently a whole bunch of different species. Sansho is Zanthoxylum piperitum and green sichuan pepper apparently may be Zanthoxylum armatum, so red sichuan pepper, green sichuan pepper, and sansho may all be different species. There is also Zanthoxylum schinifolium which is apparently used in Korean "Sancho".