Nige,
I'm not sure you can decide the report is damning or not in isolation. There is not enough information or context, or crucially DA input.
The steel bolt is DA approved, but it is NOT clear whether the DA has stated that they must not be mixed or if that indeed is permitted. QQ only speculate that it maybe an issue and it maybe wrong to jump a conclusion one way or another. To be fair on QQ they were probably not writing the report expecting someone to jump to that conclusion - they are writing it for a technically competent audience and they are highlighting issues for consideration (and future research perhaps!). You would have ask the DA whether it had been considered, or whether infact the steel bolts had been specified or torque settings changed to create an "equivalent" effect to the alu ones (possible despite the different material characteristics).
I agree it does beg the question as to where the DA information on correct installation is - but no conclusion is really reached in the report for me on this point.
My main point is that I was expecting alot worst, and you'd have to conclude that this quote....
Notwithstanding all of these difficulties, the repairs achieved by RAMS on XV250 were observed to be of a high standard. The work undertaken on that aircraft was far beyond the usual expectation and encompassed the comprehensive renewal of the fasteners and sealants at the port side rib 7 joint.
...does imply that the final result was upto scratch? Isn't that the bottom line, despite all the findings (noting a consultant will always come up with lots of findings to justify their not inconsiderable cost!)