Variability of definitions in modern textbooks and violation of the rights of students

Can a situation be considered fair when the variable presentation of definitions in current mathematics textbooks affects understanding, solution, and therefore the answer to those problems for which this is essential? It is unlikely, this becomes especially important when writing test tasks, since when communicating you can justify your own thoughts, but when writing tests this can no longer be done. Unfortunately, our students are not protected from such situations when writing the National Multi-subject Test (NMT). But if we talk about fairness, about respecting the rights of students, then the difference in the presentation of definitions should not affect the number of points scored by students in NMT who can solve problems, but solve them in accordance with the content of the textbooks they studied with. It is a shame, because mathematics experts from the Ukrainian Center for Educational Quality Assessment (UCEQA) note in their defense that assessing the quality of textbooks is beyond their competence. The question is not for UCEQA to take on additional functions of examining textbooks. The question is that writing high-quality NMT tests should include knowledge of the content of existing textbooks and take into account different approaches to definitions when writing test items, since the unwillingness to realize and correct what is indicated leads to a violation of the rights of Ukrainian students. The above demonstrates the existence of a serious problem associated with the biased assessment of applicants' knowledge when writing NMT tests in mathematics, which requires attention and the development of ways to overcome it. This may be a more responsible work of UCEQA mathematics experts in the preparation of test tasks; perhaps this should be a certain collaboration of authors and scientists in order to develop common approaches to defining concepts or their consensus when writing textbooks. The latter direction is relevant in the context of the «New Ukrainian School» (NUS) reform carried out by the Ministry of Education and Science, the implementation of which also involves the writing of a new generation of textbooks. I would like to hope that the educational community will find better directions and approaches to solving the issue raised.