My experience when I worked in support for a device manufacturer is that if you get high enough in the support tree and can demonstrate that this effects you (and the support person will also have a matrix of affected devices) you'll still get a repair/replacement outside of warranty for them bricking your computer with a bad update.
We had a specific instance where a specific budget model of phone sold by Boost mobile would brick after a specific update for people who had subsidy unlocked it and taken it to a GSM carrier such as T-Mobile (this was shortly pre-merger) or AT&T. This update rolled out about 2.5 years after this devices release, so most customers were ~12 months outside of warranty. Since the scope of affected devices was so narrow our directions from the top was to replace affected devices regardless of warranty status, and the replacement would come with a standard 30 day replacement warranty
So in short, I would expect HP to repair/replace affected devices that bricked after this BIOS update regardless of warranty status, but I would expect some amount of hassle in terms of reaching a specific support department before you get assistance and standard refusal of service for customer induced physical damage (smashed screen, smashed ports, mashed potatoes in the ports, badly bent, etc.)