这两个句子无疑都是倒装句，be后面是主语。谓语的数由主语的数决定，这是语法一致原则而不是就近原则。单看你的例句，似乎资料的解释是错误的。

但如果是这样的句子：

Next to the group of students are their teacher.

Between the blackboard and the desks are a dais.

这就是就近原则了。主语是单数teacher，谓语却用了are。估计你所说的资料是这个意思，这样的话，资料就没有错。应该注意的是，这种根据就近原则选择谓语动词的数是非正式语体，考试要避免。

存在句的谓语和最近的主语的数保持一致，也是就近原则，但这是被广泛认可的。

There is a pen and two noetbooks on the desk.

There are two notebooks and a pen on the desk.

The teacher together with his students were preparing for the competition. (就近原则，非正式语体。考试应避免。）

The teacher together with his students was preparing for the competition. (语法一致原则，正式用法。）