Does this change how insurable a home is, especially in the Wildland-Urban Interface (WUI)?

Yes, at the community level. Insurers use ISO's Public Protection Classification to rate homeowners coverage for every property in a fire district, and a poor rating can make coverage hard to find at all. Water supply accounts for 40% of that rating, measured against the fire flow a district must be able to deliver – and ISO's own schedule recognizes homes protected by NFPA 13D sprinkler systems when it calculates that requirement. ISO also awards additional credit for fire prevention code adoption and enforcement. Over time, sprinklered development can improve a district's rating, and a better rating can lower premiums for every home in the district, sprinklered or not. That is separate from the parcel-level wildfire risk scores carriers use in the interface, which measure the outside of the house and are now governed by HB25-1182.