Ice crystals forming in rapidly flowing or agitated supercooled water is a matter of common knowledge and basic physical dynamics, supported by studies on cavitation and rapid fluid impulses inducing ice nucleation.
The claim is that ice crystals can form in rapidly flowing supercooled water. This is a basic physical phenomenon (often observed in supercooled water subjected to rapid motion, agitation, or cavitation, which trigger nucleation). It qualifies as common knowledge regarding the behavior of supercooled liquids, though papers [3] and [5] provide empirical evidence relating rapid movement, cavitation, or fluid impulses to ice crystal nucleation.