A single person experiencing an error is bad luck and may go through an apeals process. Half a class experiencing the same error jeopardizes the legitimacy of the exam for enough students that they decided to handle it collectively. It may be a third party tool but it is one they are expected to use which changes things. Had it been a few students using libre office they would probably be out of luck as they would have used non standard software.

Another important note is that many exams now require digitally handing in the assignment, so the only alternative to writing the assignment in a text editor would likely have been to scan a handwritten one and convert it to pdf, if that was even allowed. So while particular hardware and software isn’t required, the limitations of the exam makes it impossible to completly avoid errors such as these.