Here's the deal: All proprietary software has that in there as well. Every piece of software has an EULA that says they are responsible for nothing. Have a look at the MS EULA if you wish, there's all kinds of shit that supposedly limits liability, requires arbitration, etc, etc https://www.microsoft.com/en-u....
You can say it all you like, doesn't make it true. I can write an EULA saying "By using this software you agree I get to take your first born child," and yet if I tried, I'd still go to jail because just saying it in an EULA doesn't make it so. You can't disclaim all warranties, all damages, etc by law. For some info on it look up the Uniform Commercial Code.
Ok well all that aside when it comes to an issue like this courts are not known for applying the law one way in one case, and a different way in another. They don't say "Oh we like this nice OSS" and give it one rule and "We don't like this mean commercial software" and give it another. Thus if courts find that software makers are liable for incidental data loss then it will apply to ALL software. OSS has no special get out clause. You don't get to have it both ways where OSS gets a magic liability shield just by putting something in a text document but commercial EULAs aren't worth the bits used to store them.
In fact, OSS will be MORE vulnerable. Commercial companies have lawyers to help them wrangle out of things. They also can always go the real contract route, where you sign an actual contract up front with them before buying (you see this with some enterprise software) which can enforce more stringent terms. OSS that is just distributed on the web doesn't have all that.