This is not entirely true.

It is not "在公司所學到的東西都屬於公司的財產，傳授所學是公司給的一個表現的機會", the knowledge you learned is yours, the work you've done is what you pay back to the company for your salary---No company would let you only learn without doing any real work, and the work you did is what they pay you for. It is not in your job description that you have to pass on knowledge, and it is not your responsibility to do so. You may do it because you want to have a good relationship with the company or the person you teach.

In one word, if somebody teaches you, that person is doing you a favor, and you should be thankful to that person. If the person doesn't teach you, it's only fair, and you should not complain for this