This is mostly a display glitch - Thrash - despite the animation - is instant-damage, and after using it, you can do whatever you want right away, including jumping.
The client would still display the thrash animation (which has higher priority than jumping), but also change your position based on the jump.
All in all, it's pretty minor - and it doesn't do much harm. Kudos for finding it, I never thought of that particular bug. However, seeing you find it fun, and it doesn't do any harm, I say we leave this in? You might get some funny screenshots out of it.