I couldn't make out what you were asking really but, having read a couple of your other posts, it seems you are talking about a front door.
I'm not aware of any reason why BC would say you can't have a wooden front door (unless you are not mentioning something in your queries), but you will need to bear in mind what your insurance company requires. Again, there isn't any reason why you can't have a wooden door but most insurance policies will require you to have a 5 lever mortice lock as a bare minimum for security purposes.
One of your other threads is regarding door and frame sizes for a 2100mm x 900mm rough opening (R/O). That size opening would only really be suitable for a 1981mm x 762mm (78"x30") door, if you are buying 'off the shelf'. The reason being that a standard exterior door frame would be approx. 57-60mm thick each side, giving you a total of between 114-120mm. Subtracting this measurement from the R/O of 900mm leaves you with approx. 780-786mm, meaning that you are unlikely to be able to use an 'off the shelf' door any bigger than mentioned above. This option also allows you to pack out the frame up to 12mm (½") each side to allow for any unevenness in the R/O.
The height of the door would need to be 1981mm because the header of the frame will again be 57-60mm thick and the bottom sill approx. 45mm. The frame sides would need to be trimmed by a few mm to meet the door size, but this would again allow 10-12mm top and bottom for packing.
Basically, you assemble the door frame to fit a 1981mm x 762mm door so that the door doesn't need to be trimmed and you will then have 10-12mm all the way around the R/O for packing and levelling the frame.
A hardwood door and frame would be a far better option for longevity than softwood.
As for your question, 'Is the frame just weather sealed?', do you mean perimeter pointing the frame with sealant/caulk or are you asking about protecting the frame with paint/preservative?