Some medical schools have outdated information on their website. Not all, and outside of the ones I applied to, I couldn't tell you which, but several have information from, say, 2011-2012 and don't mark it as such, which can be misleading for current applicants when stats are different. If you do a comprehensive comparison between data on websites and MSAR data, you'll find discrepancies. MSAR requires that information is accurate and up to date while school websites may not get around to updating as frequently.
Now, that being said, I'm not totally familiar with the Texas application process and you have some people who have been through the TDMSAS process here telling you that MSAR might not be necessary if you're applying exclusively to Texas schools, but if you're applying outside of TDMSAS, I think that MSAR is a 100% necessary purchase.