I wouldn't think of it as a red flag (to me, a red flag is something to watch for and avoid the person) but I would see it as something to keep in mind, and treat the partner accordingly.
Some conditions, mental or physical, might mean that it wouldn't really work between us, for whatever reason. If that happens, it's too bad but things happen.
However, it wouldn't affect my desire to date them. I simply would want to learn more about it to see how to help, and I would give it a try either way. Unless it's something that's potentially dangerous for me or my other partners.