分割性定语从句是不是非限制性定语从句?

不是的.
分割性定语从句是为了句子平衡而分开的.例如：
Days are gone when teachers were looked down upon.如把when teachers were looked down upon直接跟在days后面,句子就头重脚轻了.
而非限定性定语从句的作用是对所修饰的成分作进一步说明,通常和主句间用逗号隔开,将从句拿掉后其他部分仍可成立
He said that he had never seen her before,which was not true.
他说以前从没见过她,这不是真的.

嗯