I have purposely stayed away from your question, "isn't it a bit of a disservice to make any combative claims if the student never experiences anything close to combat?" Why? Because it's not what this thread was about, and I really don't want to get into a discussion about whether aikido is effective for self defence. It's been done so often in so many places I am simply bored by it, and I very much doubt anything new would come out if we were to go round and round on it (assuming of course that we disagree)
You think it's a coaching issue that waza changes under stress? I guess it's a matter of how much it changes but it's pretty much common sense that you are going to perform differently in optimum conditions than you are otherwise.