On one hand this standard provides a framework for highliners as well as slackline manufacturers to understand what components belong where and how they interact. On the other hand, it also provides a legal framework for highlines to be categorized as temporary installations (similar to Ropes Courses) according to EN 15567.
This will allow festival organisers, professional riggers and slackline manufacturers to better negotiate access and safety with insurance companies, landowners and other officials.
One crucial implication of this standard is that highline gear (including the leash) in general is not PPE, since it is not personal protective equipment, but rather a temporary structure. This means that highline gear can legally be sold without being certified according to PPE standards.
The only component in a (physical) highline rig that is PPE is the harness and other gear you bring with your harness which protects you from falling (e.g. lanyard, carabiner, etc), which can be bought from existing climbing manufacturers that hold the according CE labels with these products.