chain bush wear
Usually chain wear and needs to get replaced because of the pin/bushing wear.
What about the roller/bushing wear? Is that important to check?
Most modern chains have replaced the bushings with stampings on the side plates that hold the rollers. Either way it looks to me like wear is going to manifast itself by causing the chain to elongate. When the chain stretches, regardless of the reason, the pitch changes and it's time for a replacement.
But I don't think roller/bushing wear cause the chain to elongate. It's the pin/bushing interface that determines the pitch of the chain when stretched.