The maximum exposure during the period of a lease is whatever the excess on the policy is.
The GP comment can't be applicable to the UK.
In each case I only got the value of that vehicle as per the lowest price the insurance adjustor could find, taking the mileage and age into account. That was never enough to buy something of equal value to me, and I assume totally inadequate to pay off the outstanding loan amount.
You are required to get your own fully comprehensive insurance, and can select from the whole market. The vehicle will not be released to you from the car dealership without proof that you possess such insurance.
Please declare which country you are talking about, as the article described the UK and your claims are not true with regard to the UK.