Hello again xu zhang. Yes, for the Free Tier (public workspace), if someone goes to your workspace url, they can see your projects since they will all be public. I do want to note that the Free Tier does have one private project (called *Uncategorized*) that is meant to be more of a sandbox.
If you are in academia, you can get access to the Comet premium Startup and Teams workspace tiers for free. You just need to register with your academic email :)