Pressure reducers that modulate the flow will not necessarily "regulate" the pressure where there is no flow to "strangle".
The "Achillies heel" is this very point where there is no flow, the minutest leak across any restriction in the water feed will ultimately lead to the pressure downstream equalling the pressure before that restriction.
With minute leaks commonly encountered by debris, hair etc across even a pressure regulators seal, will take time for the downstream pressure to build up. Though the water itself can be considered incompressible, the plastic tubing we typically find in our systems does have a bit of compliance, "give", but ultimately the downstream pressure creeps up to the supply pressure.
This is well known and understood by those like myself who have practiced in these systems for capital high value kit, and there we compliment even the best of regulators with reliefs.
Elsewhere, where there is ignorance [in the true sense] or where the products being fed fluids are of more trivial value to those specifying the kit, it can go spectacularly wrong if such provision is overlooked.
The budget end products we see in this industry, operate way from best practice; that cost money even if only a few pounds.
You pays you money you take the gamble; as is so often pointed out we make our own choices. Here this bit of plastic we couple up with a hose, on multiple occasions, store where a spider might fancy using it as a home etc, so very prone to pick up spots of debris, could be considered at risk. However, one where the consequences could be huge, unless we buy tipping the van up to drain the water out some hours later, then means water flooding a caravan presents minimum consequences. As said each one their personal choices, use best practice or gamble on something falling short of it.
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