2 studies, one on hot coffee and one on hot tea, both alleged to cause or trigger rosacea or flushing. Neither study tested any other drink including food neutral hot water. It is possible that in both cases the heat caused the issues with rosacea symptoms like flushing rather than the specific drink.
It is possible to find meaningless statistical correlations between a common food or beverage and a common disease. A better test would have been to compare drinking hot beverages vs. drinking the same beverage at room temperature vs. drinking hot water vs. drinking room temperature water.