Remember when the undici guys deprecated request.formData for _all_ serverside JS installs everywhere including bun, node, deno, because they felt it was unsafe? wonder how they're doing these days.
It was unsafe and surprisingly easy to DOS servers using it incorrectly. And by "incorrectly", I mean how a lot of (most?) people used it with user data. An API that happens to be safe by accident when people use it should be deprecated.
Abusing your position as a library author isn't deprecating anything.