目前分词的逻辑主语缺失的疑惑？

Whether walking or sleeping, the subject is always in his mind.

章振邦新编高级英语语法541页。

上句walking or sleeping的逻辑主语应该是人，而主句主语是the subject,

那为何不在walking or sleeping前加上正确的逻辑主语呢？

上面句子正不正确？

Whether walking or sleeping, the subject is always in his mind.

因为主句表语in his mind可以明确提示walking和sleeping 的逻辑主语，从句省略后不会致使歧义，所以这种省略是可以同意的。