That’s a popular theory! But I’d be a lot more suspicious of anyone who says they have a summary of the movie.
Conversely, LEGO set spoilers aren’t uncommon at all–we first learned about Giant Man in CW 5 months before the movie was released the same way. Just bear in mind that the sets are often embellished in some way, often to make a scene better suited to LEGO form.
Here is the Russian site, if anyone is interested.