As per the information available from the notification by CBSE, yeah! its mentioned that those who are given special opportunity i.e., the student of 2021 who have passed the examination but due to un-satisfaction they have appeared for the improvement examination, will have the improvement marks to be the final marks. So its not clearly mentioned that its applicable for all instead its mentioned in a separate paragraph specially mentioned that 'who have passed and un-satisfied', so the possibility is the rule isn't applicable for all.

For the official notification visit the link below:

https://www.india.com/wp-content/uploads/2021/08/CBSE-2.pdf

I hope this answer helps. All the very best for your future endeavors!