Nasty bodge but probably safe. Im rather questioning the value of hardening them using tuftriding though, Its a sure fire way of making sure they let go in a big way if they do rather than gradually as they would with unhardened material and I doubt they are ground flat again after heat treating. Saying that, he seems to be under the impression its just a surface finish so showing just how little he knows about what hes doing.
As for show use only, that wont cover him or the muppet engineer who is claiming that the 8.8's he has fitted will be fine, theres a reason why VW have used better quality and no engineer in the world would accept less than stock as good enough for mods like that.
Either way, anyone who buys them has far more money than sense though at £100 as theres probably a tenner in each tops and certainly no need to machine them other than to get them flat.