Compression ratio too high for 91 octane?

Thee's a guy over on The Hamb who has an engine with a blueprinted 13.5:1 That runs on 91 pump premium non ethanol. Of course it doesn't hurt that it's a 354 Hemi either. Their chambers are very efficient.

Plus, like yellow rose always says, it's all in the tune and he's 100% right about that.