Below is a link to a recent Texas Tribune article that explains the new law and puts it into context for you.
It is important to note that it does not impact the actual date you must file a claim. Rather, it appears it was intended to curb lawsuit abuses against insurance companies arising from windfall/hail damage which led to increased rates and an unstable insurance market.
The bill appears to have little to do with flood losses that may be covered by homeowner’s insurance or business flood insurance. Rather, it reduces the penalties insurance companies face when they are actually sued, protects individual insurance brokers from the negative effects of being personally sued and reduces attorneys fees.
https://www.texastribune.org/2017/08/28/harvey-insurance-claims/