Yes, there are people who scored below 90% aiming to get into IIM Indore. Here are some things to keep in mind if you're in this situation:
It's difficult but not impossible to get into IIM Indore with scores below 90%. Attitude and aptitude both matter.
Yes indeed there are many and fortunately, my cousin happens to be one of them. However, you must keep in mind that your percentage in the CBSE exam does not show your talent. What you create in the future utilizing the knowledge you've learned is what counts.
If you'd ever seen the way notebooks are checked in 12th boards, you'll notice that most of the examiners do not check it responsibly. If you have the essential presentational and writing skills, then you might get more grades than you deserve!
Good grades do matter and might raise your chance of selection in IIM but it is not the end if you don't have the 'perfect' scores in 10th and 12th. The selection process is a secondary factor. The only aim of a good score is to show your academic background to the institute. If you clear the entrance test, WAT, and the PI as well, your previous grades will be secondary.
For people who scored below 90% and want to get into IIM Indore, their main focus will be entirely on the entrance and the interview. You have to be really good at the subjects which you've chosen or studied. It's intimidating, but not impossible so you should focus on strategizing.