Suhaib, do you mean in a job posting? You cannot see their name unless they respond to a proposal you submit. The job posting only lists their history stats and location.
Pretty missleading since in the "best practices" for contacting clients by upwork itself they recommend using the client name and avoiding generl greetings.
re: "At best you're forced to submit a generic, impersonal proposal."
Clients are not hiring freelancers based on their ability to address them by name in their proposal letter.
Proposals are not "generic" or "impersonal."
My proposals explain exactly how I am going to work on the client's project. That is why clients hire me.
The answer is no.
You do not need to see the client's name in order to send a proposal. You do not need to include it in a cover letter.
None of the other freelancers applying to the job have the client's name.
Nobody is using it.
The client doesn't want you to address her by name. She wants you to explain how you will do a great job on her project.