AWS Elasticbeanstalk CLI ignores instace type option

I have a python application that's using Flask, which I'm trying to deploy to Elasticbeanstalk using the EB CLI. I'm following the deployment steps mentioned here:

https://docs.amazonaws.cn/en_us/elasticbeanstalk/latest/dg/create-deploy-python-flask.html#python-flask-deploy

I ran the following commands

eb init -p python-3.6 demo-v1 --region us-west-2
eb init
eb create demo-env -it t3a.large

I got the following error

ERROR: ServiceError - Create environment operation is complete, but with errors. For more information, see troubleshooting documentation.

I checked the eb-activity.log and found that there was a MemoryError, which occurred because there wasn't enough space to install all the packages (as specified in the requirements.txt).

I then checked the instance type and it was showing the instance type as t2.micro. I had to manually go in to the ELB console configuration -> capacity -> changed the instance type from t2.micro to t3a.large

Seems like the CLI ignored the instance type flag and it didn't throw an error or a warning. How do I specify the instance type for my application?