No, that's wrong. The claim is that the bred U-233 will be contaminated with U-232, which is very hard to get rid of, and has the hard gamma emitter Thallium-208 in its decay chain.
How hard this would be to separate depends on the type of LFTR design you're using. However, you could also include some thorium-230 in the fuel mix to denature any protactinium produced, so there's really no way around having U-232 mixed with the bred U-233. Here's a blog post with more details on the entire process:
http://energyfromthorium.com/2006/10/06/denaturing-thorium-w...