Actually, in certain materials such as 「オーズ 電王 オールライダー レッツゴー仮面ライダー」and 「ライダー40年の歩み 40YEARS CHRONICLE, it is confirmed that the Wataru and Kenzaki who appeared in Decade were indeed the original. Of course, other materials say the opposite, but I feel its still worth mentioning.
But this is a wiki, meaning that any piece of official information should be presented to the audience in some form. I don't like how Toei presents it previous protagonists as anti-villains or cannon fodder in sequels, but its simply what's shown on screen. Plus, let's face it, with the franchise lasting for about half a century as of 2020, there is bound to be contradictions from time to time.
Dude, it isn't false information if the creators (such as Shōji Yonemura) were the ones who said it. The reason why some materials suggest the whole A.R thing is likely to appease fans who disliked how Kenzaki and the others were portrayed as, with me being one of them. But nothing was explicitly confirmed in these sources of info, just implied.
Plus, I'm sorry to say this, but I don't think Kamen Rider Decade's plot is exactly a model for cohesion, especially due to its numerous plot holes, plot contrivances and deus ex machina. The same could be said of most crossovers, if anything.
This user was banned due to vandalizing the pages. Could you please help me clean up the mess he left to us? I even noticed that he wasn't only using wrong template, but also replacing HQ covers for DVD/BD with LQ ones.