Viva prep helps you to feel ready for the viva.
Learning about expectations helps you to feel ready for the viva.
Exploring who your examiners are (a little) helps you to feel ready for the viva.
Rehearsing the kind of work you will need to do in the viva helps you to feel ready for the viva.
All the various tasks are there to help you towards feeling ready.
But you don’t want to feel ready for your viva: you want to pass your viva.
That’s OK. Preparing will help you to pass, learning expectations will help, exploring your examiners and rehearsing all help you pass.
Except you don’t want to pass: you really want whatever you’re aiming towards after your PhD is complete.
The PhD is a goal, not the goal.
A few thoughts: can you do viva prep in such a way that it benefits your real goal? Can you organise your prep to leave space for working towards your real goal? And viva prep is easily defined, but have you clearly set out what you’re really working towards?