He has zero history of leaking stuff like that and I have been lurking on AT forums for nearly 8 years,so if suddenly has got world exclusive news that is quite a change TBH.
That is where he mostly posts,and I know you post on there too. Remember on this very forum people mock Wccftech for their "leaks" saying they use random stuff mentioned on forums,and even on AT forums they have actively mocked people who have come up with "leaks" like that. You don't believe me - look at the Vega thread on there where they attacked one of the Italian leak sites,even though they have on and off got some things correct(and other things entirely wrong). It even happened over there when CPC got that leaked Ryzen sample and some people were dubious of the results,despite them leaking the Athlon 64 results accurately years ago.
The issue is if people overhype the clockspeeds of Coffee Lake like this,and it happens that his exclusive is not quite right,people will end up having a go at Intel,not all the rumour sites. Remember the over hype for Skylake-X people did before launch?? Half the negativity is because enthusiasts did that,and not Intel.
Now he might be right so I would not discount it entirely to be fair to him as he might have some mate who works at Intel,but until we start getting more stuff leaked that actually confirms his numbers,I would just wait for some more sources to pop up. If he does put some screenshots up that would be even better.
Coffee Lake and Zen+ after all are top of my list for upgrading my IB Core i7 next year and I don't really overclock that much(mini-ITX system),so high stock clockspeeds would be great for me.