In Hong Kong, is a medical questionnaire needed as part of buying travel insurance?

A Hong Kong resident and citizen, my grandmother bought travel insurance:

1. that exclude pre-existing medical conditions that she does have

2. from her agent with AIA in Hong Kong

3. at a cost of $600 Hong Kong Dollars (around $77 USD)

4. for 14 days

5. for travel to North America.

But shockingly, her agent told her that no medical questionnaire was needed and thus she did not complete one. Is this correct? This agent appears wrong, because without a questionnaire, then how is it possible for my grandmother to be (e.g.):

6. reassured coverage, to prevent the insurance company from exploiting pre-existing conditions to deny genuinely new medical problems during her travel?

7. priced correctly? $600 HKD appears far too cheap.