Secondly, if students think learning pinyin is learning Chinese, they’ll have a false hope that they can speak fluent Chinese without the need of learning Chinese characters.
Although pinyin helps students get started quickly, it can not get students to a relatively high level. When students learn more words, pinyin becomes so look alike, and so confusing. For example, does “shi li” mean “strength” in Chinese?
Thirdly, because tones are so visible in pinyin, they are often unnecessarily over-emphasised.
There are many jokes playing around tones of pinyin. For example, a guy wanted to order dumplings in a restaurant. Unfortunately, what he said was “shuì jiào” (to sleep) instead of “shuǐ jiǎo” (dumplings), so he got slapped by the waitress.
After teaching Chinese for many years, I find there are many problems with this kind of jokes. I suspect that it must have been written by someone who had not learned any Chinese at the time.
To conclude, pinyin itself is not Chinese. It is a representation of what Chinese sounds like.
Learning pinyin is not learning Chinese. Learning pinyin is learning a tool which helps students learn how to speak Chinese. Also, relying pinyin as the only means of learning creates hurdles in the long run.