My concern would be where the plastic tubes meet the turns. Certainly there is stress: fluctuations in water pressure, temperature, sunlight, corrosion, UV damage, in addition to a structural load at the joint. Think about a radiator hose for a moment. There is serious structural strength built into them, and even still care must be taken not to overtighten the clamps and compromise the structural rigidity.
Certainly, the PBR components must endure more severe stress than a radiator hose, but I wouldn't trust Dennis' bags as my radiator plumbing.
The manufacturer can talk about their material lasting, but was the science done to determine if it can withstand the stresses of this application?