I bought a ton of samples as well and I feel the same as the OP. I was actually taken aback when I saw I could only post reviews for the teas I purchased as I was thinking, 'What if I tried this tea at a friend's house or something?' Usually a person only bothers to post a review if they have a tremendously positive or negative experience and well, if it's the latter you certainly aren't going to be buying it just to write a review.
Though I'm not too bothered by this either as I do see it as a safeguard as you could have someone who tried Chamomile from another vendor and types a review based on that impression which wouldn't be dishonest but not entirely relevant.
One issue I do have though is that it appears to me (Correct me if I'm wrong) that you only get the discount from writing a review when your cart is full and you intend on ordering during that same session. Is that right? I'm thrilled we even get an incentive to write a review and applaud the site for that (I never buy any unknown product without checking reviews online for anything) but would like to be able to write my review when inspired to do so as opposed to holding off until my next order. I may be wrong, I don't know, but if not, yeah.