That’s your thesis.
Before the viva they have to read it, think about it, make notes, think some more, read papers and write reports and then think some more because that’s the job they’ve agreed to do. That’s the role of the examiner. They have to examine your thesis so they can then examine you in the viva.
Whether your feet are firmly planted in one discipline or you’re playing Twister between two or more, your examiners will do what they need to do so that they can examine you properly. You might have expertise that spans multiple areas; theirs might be more concentrated. Still, they will do the necessary work to do the viva well.
Examiners are never perfect. They’re professional. They’re prepared. But they might not know as much as you, or be familiar with all the terms and ideas that you use. So they do their homework. That might put them out of their knowledge comfort zone, but they still do their homework.
Expect them to be ready, whatever their background.
Expect that you will be too.