Keep in mind that the purpose of coinsurance is to encourage policyholders to adequately insure their property. Most losses are partial losses. Without coinsurance policyholders may intentionality under insure gambling that they will only sustain a partial loss and still recover their full loss. This defeats the basic insurance principal of spreading the risk over a pool of policyholders.
A good broker will assist their client with determining adequate limits to satisfy the coinsurance requirement. If the broker fails to adequately advise the client about coinsurance and the need to insure to full value they could be on the hook for the shortfall. I suspect a lot of brokers in the Caribbean are sweating about this right now.