All the versions I see on IMSLP and other places don't even have a key listed under the title. It's just Toccata. This sure looks like a major error, I mean a c major error....haha
Haha, I don't think Russian editions are famous for their accuracy. Plus they have a problem with letters. They probably meant S major Having said that, the first big climax IS in C major. Doesn't make it right of course.
The funny thing is, at first I was going through noticing all the chromatic-scale figures and otherwise trying to come up with rationalizations that would justify C major. Then I gave up and suspected an error. Glad to know I am in good company!