Wrong.
Many people have been demobbed due to failing MATTs, especially MATT 1 - shooting, and MATT 2 - fitness.
Units are entitled to refuse people not up to the standard. The 4 mile TA CFT is easy, but bear in mind you are at RTMC for about 2 weeks, then a week at OPTAG, then out to your receiving unit who may hit you with an 8 or 10 miler upon arrival. If you're not fit you'll just give them the impression of being a W*nker. Some units will send people home for Demob who are not up the job.
I think RTMC now hold failures until they pass (at the units request) - lots of beastings for the fat boys then!
Best bet is to sort your fitness out or grit your teeth for an hour. Remember pain is only weakness leaving the body.