No, the electrician didn't fit the fan, nor did he install most of the electrics. The builder installed the fan. However, the two of them work in unison, and the electrician makes the final connections etc after checking out the builder's work at different stages. In effect, the builder works under the supervision of the electrician. Of course, the electrician is taking full responsibility for signing off the work, but that is his own decision based on years of experience gained from the two of them working together.
In rare instances, as in this case, the electrician has to correct or undo something that the builder did wrongly. I am the householder, and have a good relationship with both of them, so I am in on their discussions. I was the one that chose the fan, the builder fitted it, and the electrician then came along to sign off everything electrical. But the electrician has to revisit since he says, wrongly it seems, that the fan must be replaced. Yes, the additional cost should be bourne by the builder, but only if the builder has made an error in the first place.
