In many sources related to jet engine thrust calculations such as https://www.jet-x.org/a8.html , pressure thrust of a module such as combustion chamber, nozzle or compressor, is calculated by front and rear cross sectional area of them (including holes at their center) and flow pressure at front and rear of them.
If they were a complete solid disc without any hole, I could understand this calculation.
However, for turbine in an example, it has a hole at rear and front, so either pressure at rear can't act on the hole at rear or pressure at front can't on the hole at front. In my opinion, these holes should be taken out of cross sectional area term.
Why do we think as if fluid pressure is able to act on the whole cross sectional area including holes at the center whereas they can't physically?