Why do you pre-exhaust?
He's using 5kg dumbells for laterals which suggests beginner to me, I wouldn't think anything special is required.
Why do I Pre-exhaust?
Because I like the feel of it, I like the results, I like the change.
And most of all it works for me, i love fatiguing the muscle on a single joint exercise that doesn't really get worked on a multi joint exercise to the same degree and feeling that muscle burn with pain that you don't experience when just doing the multi joint exercise.
But the key is, you need to move extremely quickly between the two and one set is enough on the Pre-exhaust, if you need two, you didn't go hard or heavy enough.
After you've been doing workouts consistently for thirty years you like to try different things.
And lastly, Who gives a shit whether he or she is a beginner, I'd say they have got a few years to work out what works for them.
Using the old blanket statement " biuld a base" is not helpful to a young bloke who is keen to experiment.
You know, it's really all about the journey, not the destination in my view.