Apparently, all those who felt left out of the "short proposal" campaigns have now jumped in on the subject. Even Upwork sends me "Upwork 101" (why?) information, including, "Keep your pitch short and direct, ideally 100-300 words."
I am well aware that "short" is the mantra, and has been for some time. However, there are clients who are concerned primarily with profiles and others with proposals. I'm not suggesting writing a novella, but some jobs require more than you can say concisely in 300 words.
If a client wants a basic job, with nothing complicated, and nothing to explain, then there isn't a lot that needs to be said. However, if the client has a more complex project, there may need to be a lot more said. Each freelancer needs to decide what works best for them. I send some clients a short, direct proposal, and other clients receive a more in-depth one. I let the clients know what I can do for them, and it may take more words to explain.
I am Top Rated and have completed 100s of projects on Upwork.
I have to work at not exceeding the 5,000 character limit on proposals. This might put off some potential clients, but I am interested in working with the clients who are detail oriented and appreciate knowing how their job will be fulfilled - what they can expect from me and what I expect from them. Many such clients tell me they appreciate the details I provide.
There is no one-size-fits-all approach to successful proposals.