There is really no tax benefit for any international student to apply for TFSA. The main reason is that international students most likely have enough tuition credit against any sources of income. As I said before, financial institution might encourage students apply for one. The reasons may be:
1. Student will most likely not going to be liable for tax, let alone interest on the $5,000 savings. (interest would be less than 100). Therefore, even though international student applies for TFSA and CRA could disallow the tax free benefit, they will still not going to be taxable anyway.
2. Financial institution are trying to promote sales and other types of service.
I am not gonna argue with your so-called source of information. Information is information. Tax legislation is another story.
To the last comment above, no one is making that assumption. Plus, you don't even need a tax expert for a basic TFSA question.