They probably forgot it, just like other things.
That was my initial thought, but wait a minute…
Starting in Patch 28.6, Whizbang the Wonderful will temporarily function in the same way he did at launch (decklists from The Boomsday Project). He’ll be reverted in a major patch after the Fast Forward Twist season ends.
The next major patch, 29.0, was still in March, right? Thus, the reversion should be expected in 29.2.
There’s a new one there, so probably not, or else who’d buy or craft the ‘reprint’? 
Maybe it’s just that only Standard deck recipes are supported [1,2], so it’s more of an oversight than an intention.
[1] https://hearthstone.wiki.gg/wiki/Whizbang_the_Wonderful
[2] https://hearthstone.wiki.gg/wiki/Deck_Recipe