Most GPU vendors and their partners do not state clearly how many displays the device can use, in fact most people do not know that AMD Radeon cards depending on the model can drive up to 6 displays. Nvidia GPUs can drive up to 4 in most cases.
On INTEL GPU is also a mystery unless you check carefully.
Avoiding this issue is quite difficult as well. For example some vendors can provide a GPU that can handle 6 displays but they can easily limit this feature as it is not in their interest to provide such support.