It's not necessarily "completely waterproof," and attention needs to be paid to "waterproof details":
The core of WP is the "high water pressure resistance of the fabric itself." However, the product is made up of multiple components, such as seams, zippers, and pockets. If these areas are not properly treated, such as unsealed seam holes or detached zipper waterproof tape, water may still seep through these details even if the fabric meets the waterproofing standards.
Therefore, high-end WP products undergo additional "seam waterproofing testing," such as sealing seams with tape and "overall rain testing," to ensure that the joints are watertight.
