Nope, not a design issue...if there isn't a bushing there, there should be. See #8 inside of #7 and #13 in this drawing...
It's likely still there but has worn out and the inner part separated from the outer part. Here's what they look like:
100_8185 (Medium).jpg
CC charges more than $20 each for these things, so if you have multiple tractors, it makes sense to order them directly from the manufacturer for nearly 10x less.