That doesn't mean it can't flood!! If you look at the places in Northern Caves which have flood warnings, they tend to be places where the risk and/or degree of flooding is significant.....e.g. diccan, washfold, marble steps, bown scar, sleets gill, crescent etc etc etc.
When we went down Hangmans in February, water levels were pretty low and unprintable passage had lots of airspace. In normal to above average conditions, the crawl can have a very limited airspace and in wet weather would, i imagine, become very desperate indeed or impassable due to run-off flowing in from the entrance shakehole.
Like most others, one for a settled day