Are fabric (polyester) liners actually waterproof?

Specialist-community consensus is that good polyester liners are water-repellent rather than truly waterproof: water beads and runs off but the fabric can feel damp. r/ZeroWaste and r/homemaking commenters report years of trouble-free use if the liner hangs inside the tub and is washed periodically. A minority of Walmart verified reviewers on cheaper fabric liners report water passing through, so weight (GSM) and a tight weave matter.