I don't think there's that much of a difference between Sativa/Indica... definitely not enough for you to not notice it!! I couldn't tell the difference until after I started getting stuff at a dispensary and KNEW what it was... the difference is subtle.

So, no the herb is likely weak or more likely premature! A lot of people sell premature stuff which hasn't had the chance to develop peak potency. Are they light/airy buds that are mainly leafs and pistils?

Also, it's probably not a legit trainwreck cut if he's calling "medical trainwreck" as a strain name. Not sure if you were just clarifying that it was for medicinal use or if that was a strain since you referred to it as M.T.