I read the Otar book several years ago. I could be wrong about this, but from what I recall, the "rebalance in presidential years" suggestion was based on what provided the best returns over the last X decades (it was compared to several other rebalancing schemes). It wasn't based on any kind of logic as to why that was best. I don't think the differences from the various approaches were significant.
And since the future may not be like the past, I wouldn't feel obligated to follow that suggestion.