Why does one have to use warm water with water flossers (e.g., Waterpik)?

I read in a few places that one has to use warm water with water flossers (e.g., Waterpik). Why wouldn't cold water be ok too?

E.g., from https://www.waterpik.com/oral-health/blog/waterpik-mouthwash/ (mirror):

all you need in your Water Flosser for clinically proven effectiveness is warm water

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