My own definition does not matter. Swiss law matters:

'The order may require real-time surveillance to be carried out and the handover of the retained secondary data of telecommunications from past communications (retroactive surveillance).'

https://www.admin.ch/opc/en/classified-compilation/20122728/...

The question is not whether ProtonMail has access to user data. (They have, you are absolutely right.) They question is if they perform real-time surveillance, i.e., lawful surveillance (whether voluntarily or not).