Projects in Semrush can only be created for domains, not subdomains.

This statement is false. Semrush Projects can be created for both domains and subdomains. When you set up a new Project, Semrush allows you to specify the exact URL you want to track, whether it's a root domain (e.g., example.com), a subdomain (e.g., blog.example.com), or even a specific subfolder or URL (e.g., example.com/category/product-page). This flexibility is crucial for businesses that manage different sections of their website on subdomains or need to monitor specific parts of their site independently. Therefore, limiting Projects to only root domains would severely restrict the tool's utility for many users.