Based on the way I wrote it, you are right. The way I wrote it sounds as if I found absurd that not every person can go airside.

What I wanted (and obviously failed to say is): in Zurich any *passenger* flying that day can access any air-side departure part of any concourse of the airport. In Paris passengers on the day of departure can only access the concourse/terminal they are flying from.

What I find absurd in Paris are two things:
1) The reason given by staff for why a ticketed passenger cannot enter another terminal/concourse: "for security reasons". To take an example: I want to go to the lounge in 2F, but my flight leaves from 2E. What exactly is it that compromises security if I am in the air-side departure area of 2F even though my flight leaves from 2E? Why does the fact that I am air-side in the terminal from which my flight leaves make me an un-dangerous person, but I suddenly become a dangerous person in a different terminal only because my flight does not leave from there? Shouldn't the criteria for whether or not someone is dangerous be whether or not that person passes the security controls successfully, rather than whether or not his/her flight leaves from that terminal?

2) Immigration officers refusing entry into the air-side when the boarding pass doesn't show a departure from that concourse/terminal. Since when is final destination a criteria for whether or not someone is allowed to leave the country? What matters is someone has travel documents that are in order and allow passing the border, but not where that person goes after having passed the border. So basically, by refusing people who leave from another terminal the immigration officers are not applying immigration rules but some other rules.
That becomes absurd when you then realise that the rule of not being able to pass immigration with a boarding pass from another terminal is only applied to passengers who pass by a manned counter. Those using PARAFE biometric gates with the right travel documents are allowed to pass the border without their boarding pass and final destination being checked. There shouldn't be different criteria for passing the border depending on whether you pass by a manned agent or whether you use PARAFE.

The Zurich absurdity really is absurd: why are people that go through one and the same security filter in JFK and board their flight at one and the same concourse at JFK Terminal 4 treated as "clean arrivals" when they arrive on board an LX plane but as "unclean arrivals" when they arrive on board a DL plane? Shouldn't security procedures in the departing airport be the criteria for whether or not an arrival is "clean", rather than which airline is being used?