They are totally different as guess you are aware.
Travel insurance covers delays, lost property, and emergency treatment following a health issue or accident, also change of flights due to a family emergency.
Health insurance are generally for 12 months, only cover health. But in a different way, if you needed an op for example like hip replacement, cataract that wasn't urgent it's covered. Some health insurance also cover you as an outpatient and for dental care for extra premium. The premium therefore are alot more depending on any medical history, age etc. Read the small print too if riding a motorbike, mine only pays 50% of medical costs even as a passenger
I think getting drilled at immigration is far worst. Prepare a visa application at ones leisure from home, even ask a friend for guidance is a better idea