We're working out what we think - we'll add our view here!
Fjällräven says:
Extra ground sheet for Keb Endurance 3 and Abisko Endurance 3 that covers the entire tent footprint, including vestibule. Made from durable, waterproof nylon fabric with PU coating. Protects tent floor and equipment against abrasion, dirt and moisture – practical when pitching tent in stony, wet or muddy conditions – and also reduces condensation inside the tent. Attaches with toggles.
We're working out what we think about Fjallraven's Endurance 3 Footprint, we'll add our comments here in due course.