I'm sure the answer is "No, all castor oil is not the same". However, if I was mixing fuel with say, 17% Klotz and 5% castor, I'd use whatever castor I could get, at least generic or medicinal types. Dunno about the motorcycle/Kart type oil, but I think one of those would be Klotz "Benol", which I'd use in a heartbeat. The reason I'd use any castor in small doses is that Klotz has considerable detergent action and should keep the engine clean. Would I run straight medicinal castor, or 20% medicinal castor with 5% Klotz? No, probably not, at least without some testing on an inexpensive engine. Especially on a new engine of any sort.
Many decades ago, I bought a can of castor from the motorcycle shop...Blendzall. It smelled of Nitro Benzine, which we know makes it mix better with gasoline and nitromethane. Also reduces pre-ignition, if that's a concern. I think it might help with straight (no nitro) alcohol fuel, IF you are pushing the compression ratio to the max for F2A or F1C. But then you can't get Nitro Benzine anymore, so if you can get Blendzall, it will have something else in it. FWIW, the plastic bottle I put the Blendzall in has collapsed in volume from (apparently) the NB seeping through the pores of the plastic bottle/lid/seal. No leakage is apparent, anyway.

Steve