That is what is written in the policy.  I give you an image that is pre-configured that upon instantiation, contacts the ALICE central task queue to obtain a workload.  It does NOT contact the batch system of the site.  Explain to me, after re-reading the above excerpt from the policy, how this is not banned!!!  The image is pre-configured to obtain a workload!

Let's make this very concreet:
- The VO software contains a script called /opt/bin/alicepilot.
- The user specifies in the JDL that this script should be called on boot.
- The site contextualizes the images, in this case it means that a boot script is inserted that calls /opt/bin/alicepilot with user priviliges.


So, it is perfectly possible to get work from a pilot job framework with site contextualization.
What am I missing?

it is perfectly possible to do it via your way, it is also possible to do it my way (the image is simply a pilot job and needs no interaction with the JDL ... specifying the image to run is enough).  But my way is banned, why??

Because your way to obtain the workload will be acceptable on some sites but not on others, you cannot demand from all sites to support your way of obtaining a workload. With the contextualization as proposed by the working group it is up to the site how they eventually will obtain the workload. This procedure will be very different from site to site and depends a lot on the way VMs are integrated on the site infrastructure. CERN might choose to obtain the workload by connecting back to the batch system, Nikhef might do it in the way I propose above.

So, I see what you mean by banned now: the policy indeed bans the possibility to impose a specific way of obtaining your workload on every site. I think that is a good thing.