You are way over thinking it! Mark Gurman has inside information and it’s unlikly that there will be no hardware at WWDC. Doesn’t mean 100% like I said BUT it’s unlikely that there will be hardware. WWDC is often a software focused event anyway, last years updates was a one off and not somthing we will see every year (in my opinion).
Software-focused, yes, but that statement alone doesn't mean much. The focus can be on software (and usually is) and there can still be a good number of new hardware announcements. If we look back at all the hardware announcements we had at WWDC over the years, we had:
2003 - Power Mac G5,
2004 - 20" and 30" Apple Cinema Displays,
2006 - The Mac Pro,
2007 - The iPhone release date was announced,
2008 - iPhone 3G was announced,
2009 - MacBook Pro spec bump for 15” & 17”, 13” MacBook spec bump, also rebrand as "Pro". The MacBook Air got a spec bump, and we got the iPhone 3GS,
2010 - announcement of the iPhone 4,
2012 - MacBook refresh and Retina displays on the new MacBook Pros,
2013 - MacBook Air spec bump and 2013 Mac Pro,
2017 - New MacBooks, MacBook Pros, iMacs, iPad Pros, MacBook Air spec bump (small), HomePod and iMac Pro announcement.
And these are just the "big" announcements, not counting minor stuff like some new accessories, cables, colors or price adjustments which we got at almost every WWDC in some extend.
Again, this is not to say that Gurman is wrong – but I agree with TheralSadurns that he has phrased that passage quite vague, most likely fully intentional, and it's a logical implication of that that his sources might not be entirely sure about it themselves and he probably doesn't want to jeopardize his track record by making any definite and precise but potentially false statements about them.
If we
do get new MBPs at WWDC, then he could essentially come out and say "Well I only called it
unlikely so I wasn't wrong, and in regards to these products not being ready until later this year, I was solely referring to the non-Pro MacBooks for those". And if there are no MBPs at WWDC, he can simply claim "See, told you so". Whereas if he simply stated in the article "There won't be new MacBook Pros at WWDC 2018" and that turns out wrong, there is no way to straighten up that statement in retrospect. He goes into a lot of detail about several other predictions like the AR features or the digital health thing, so it's not like he doesn't know what he's writing about and how he needs to phrase things.