I don't see why it is 'worthless'. It is merely a documentation of the fact that the electrician 'is not to blame' for doing, at the request of a customer, things (which don't make the installation any less safe than it was) that, having been advised otherwise, the customer still wants done - which I would have thought was what both electrician and customer would want of the document.An EIC or MWC covered in get out clauses is a worthless document.
Is it any different from a builder saying/writing "I've replaced your broken tiles, as requested - but, as I told you before I started, the whole roof is iffy, not up to regulations, and really ought to be sorted out"?
Kind Regards, John