是不是只有be doing出现才是现在进行时,所以说be doing构成现在进行时

be +doing 不一定是现在进行时态啊,有可能是动名词做表语,例如
Her job is raising pigs
His job is washing dishes
His hobboy is collecting stamps
以上都是动名词做表语,说明主语表示具体内容