是的。网友理解正确。如果，一个单词既是连词也是介词，那么在使用时，优先考虑介词用法。就是说，如果省略主语，它一定是介词用法，不是连词用法。按照介词后接动名词处理。例如，before 和after 既可用作介词，也可用作连词。since 也是同样的情形。注意以下句子正误：

Before sent to hospital, he felt very upset.（误。连词省略为错误）

Before being sent to hospital, he felt very upset.（正。介词）

Before he was sent to hospital, he felt very upset.（正。连词）

After sent to hospital, he felt much better.（误。连词省略为错误）

After being sent to hospital, he felt much better.（正。介词）

After he was sent to hospital, he felt much better.（正。连词）

Jim has made many critical choices since being told of his illness.  

自从得知他的病情以来,吉姆做出了许许多多关键性的决定。

Since being elected manager, Robert struggled for employees' respect.  

自从当了经理, 罗伯特努力去赢得员工的敬重。

以上两句，since 用作介词，being 不可省略。