Reading under the following link: 

https://79610--ocpdocs-pr.netlify.app/openshift-enterprise/latest/edge_computing/image_base_install/ibi-preparing-for-image-based-install#cnf-image-based-upgrade-seed-image-config_ibi-preparing-image-based-install

There's a note:

The proxy configuration on the seed and target clusters does not have to match.

We should expand on it a tiny bit.

The configuration doesn't need to have the same proxy servers, but it needs to be either enabled or disable in both: seed/target