I cannot speak about that specific tent but my experience is that with a double wall tent, touching the sides in not an issue, if it were I would be in big trouble. I sleep with my dog who is constantly either touching or resting against the inner tent wall. We have been in some very heavy downpours and stayed nice and dry.

Back in my Boy Scout days we used Egyptian Cotton tents and being single walled we had to be careful not to touch the sides when it was raining. A nylon tent with a good fly is a totally different matter.