Yes Tin will be produced as a secondary product. The process for extracting both tin and wolfram is very similar, due to both having a similar high SG. The main difference between hemerdons Mill and Crofty/Geevors old mills is the DMS at Crofty/Geevor was used for a rough seperartion - the float was reject, the sinks were processed. At Hemerdon the sinks are ultimately product - there is little processing behind it. The undersize which doesn't go to the DMS is tabled - At crofty the sinks were ground, classified and tabled. Crofty had somewhere in the region of 100 shaking tables - Hemerdon has 3 and the mill has over 10 times the throughput! As someone said if it was ground, being so heavily Kaolinised you would end up with a lot of slimes, which absolutely screws up shaking tables as the materials can't seperate.
Once the seperation at Hemerdon is done, it is ground, it then goes through a froth flotation section (To remove the Arsenic - Again like Crofty) followed by a final magnetic seperation to seperate the tin from the wolfram (Wolfram is more magnetically susceptible than tin), again this was the final stage at crofty who used to sell small amounts of Wolfram.
I think you could put Crofty's ore through Hemerdon and get a product at the end of it, but your recovery percentages would be apalling in comparison to Crofty and ultimately Wheal Janes Mills (Wheal Jane was very different in that the major seperation process was froth flotation due to the sulphide nature of Wheal Jane).
The basics of seperation is the smaller you grind, the more mineral you liberate from the waste, which means the more you recover. However if you over grind you screw it right up! The other thing to remember is the relationship between grinding size and electricity cost is an inverse square relationship - you half the size - you quadruple the power requirement!