What's the difference between Fly and Flyctl?

I have two CLIs installed, fly and flyctl. which tells me that they’re two different binaries (both in /usr/local/bin) and not just aliases. I installed with brew: brew install superfly/tap/flyctl

Basic things like fly logs and flyctl logs do the same, and both -h flags give the same help information (both identify themselves as flyctl here actually). Dumb question: are these completely interchangeable? Is there ever a reason to use one or the other?

flyctl is the actual binary and fly is a symlink to flyctl. We’ll likely switch to fly at some point and wanted to support both in the meantime.