While I say that in the previous lecture that EBS volumes cannot be attached to multiple instances, I know it is not true for io1 and io2 volume types: this is called the EBS Multi-Attach feature.
From an AWS Cloud Practitioner exam perspective this out of scope for the exam.
In order to keep the course simple and accessible, I have left out this feature from the course.
If you are curious to learn about EBS Multi-Attach, you will find it in the AWS Certified Solutions Architect Associate course, or in the AWS documentation.
Happy learning!