I wouldn't called it a bug actually. Not the complete SVG standard is supported according to the ePUB specifications. I have no time to look it up, but I would be surprised if switch was supported in the specifications.
I looked it up. The SVG 1.1 specs must be supported, with the exception of animation and scripting. I assume that switch falls under the scripting.
If you want to look it up yourself, check the spec