Yeah I don’t get why they do it, Dendrite knows more about those stations but I know several local PWS in the area that seem fine in light to moderate events but then in any torrential rain they seem to tick upwards real fast.
The Vermont Electric CO-OP has one that in most rain events seem ok, maybe a tad high, but then in a heavy rain event they rise much faster than others for whatever reason. Another one in Johnson and one in Hardwick always stand out around here, this morning they are about an inch higher than neighbors. Like you said there’s no weird spikes, just gradual increases but the rain rate is always higher.
Wait till tomorrow and see what that guy at 1800ft reports, it definitely poured hard after 7am.