定语从句与分词的转化

定语从句与分词的转化
有这种说法：“在关系词充当定语从句的主语的前提下,如果从句的位于市实义动词,那么此时的定语从句简化后一定就是分词短语,包括现在分词短语和过去分词短语.”
请问,一定要是实义动词才行吗?
比如The men working on the site were in some danger
换成The men who were working on the site were in some danger
如果用The men who are good for people are standing there
可以换成The men good for people are standing there
如果可以的话 上面的论述就不对了哦?因为are 不是实义动词啊!