Doubt it, since they didn't care about spoiling Vikavolt, Brionne and Primarina.
I don't think it's simply that they don't care about spoiling things (they don't), I think its a matter of "when they want the spoilers to be revealed"
Vikavolt had to be spoiled simply because it's a location based evolution, just like it would be pointless to not reveal an evolution for a stone based/item based Pokemon. Brionne felt a little tacked on for the sake of it, but they did want to illustrate Lana had purpose in the episode.
As for Primarina, it was only spoiled in the same vein as Ash's Greninja was (if we do not count the XY&Z poster) it was revealed within the episodes of the show, unfortunately I do realize yeah it was spoiled in the poster, so not the best example, but it was foreshadowed within the show. Primarina being spoiled in the preview of the episode, well I'm not sure how to qualify that other than yes, they spoiled when they wanted to spoil it (since the only reason to suspect Primarina was because it was a Lana episode, and Pokemon Fan said something would happen to Lana (aka one of her Pokemon evolves), especially with the whole debate of Lana catching Kyogre instead of Primarina when the episode was first revealed.
So for Incineroar, maybe they decided they wanted to keep Incineroar a relative secret and only want it to be revealed as close as possible to the actual air date?
Why? I don't know maybe Ash with Incineroar is a much bigger deal than anyone else, and want people to be surprised rather than already expecting it.
Who knows, because their inconsistent when it comes to spoilers. I miss the spoilery openings/endings.