hello /fa/, im thinking about contracting a tailor to make a similar coat from the picture starting from a butterick 6844 pattern

i allready have the pattern but after watching the movies again, except for the collar and the shoulder/arm part, i cant see any seewing line in the back or anything...and the pattern clearly should have one in the midle of the back

is it possible that the whole back of the coat is a one peice AND is it pratical to have a 1-peice back or should i follow the pattern

thx in advance