Why would that be the case? The POH has no legal bearing whatsoever when it comes to describing the actual performance of an experimental aircraft. Matter of fact, many builders will state their POH is a cut-n-paste from one they found on the internet. But an aggressive attorney may indeed try to tie the builder to the POH as a guarantee of the aircraft's performance and operation.
Even if no builder has been "successfully sued", I don't want to even think about the expense and trauma involved in defending against a suit even if invalid.
When I sell an aircraft I have constructed, it is sold "As Is, no warranty or guarantee of airworthiness expressed or implied", and with no POH (even if I had one...).