There was another thread about the camera app having an "enforced" telephone recently for a different Samsung model, so I think it's probably a standard Samsung thing now (it's not an Android thing, since we have 2 phones in my house running Android 11, one of them on the July 2021 update, and neither has a camera app that can even be granted phone permission. Whatever this is, it's Samsung).
The reason isn't clear: phone having camera permission makes sense for video calling, but camera having phone permission doesn't add up unless you can initiate a call from the camera app. It will need microphone permission in order to record video, but that's a separate permission (to the extent that my Phone app has separate "phone" and "microphone" permissions). But if there is a reason for it I really doubt they'll tell you. Sadly there is plenty of precedent for manufacturers granting their own apps unnecessary and, in some cases, non-deniable permissions (Google as well as OEMs being guilty). Whether this particular permission is due to some feature nobody has been able to work out, simple incompetence on Samsung's part, or some internal policy of granting themselves extra permissions routinely so that people get used to them and don't question it any more, I have no idea.
(Incidentally I don't know anyone who makes video calls using the phone app: people who make video calls are in my experience are invariably using a messaging app to make those calls rather than the phone app (or, if they are older, Skype

). In fact I'm not even sure which if any UK networks even support cellular video calling: it was heavily advertised by one carrier many years ago, I think as part of their 3G rollout, but was expensive and never caught on, and I know that my own provider doesn't even offer it.)