Yes. The National Institute of Open Schooling is a Government Organization which have the equal authority just like CBSE or ICSE. Therefor the marks acquired in NIOS exam are definitely valid for the NEET Exam. Through NIOS, many students who were not able to get the percentage greater than the required percentage can also score good in this exam for clearing the eligibility criteria.

Since, if they go for the improvement exam, they would have to wait for a whole year for the exam. But through NIOS, you can appear in the 12th exams any time,irrespective of whether you are a distant student or not

let me know in the comment box if you are having any further doubts

hope you find it helpful

thanks

Good Luck!