Only one piece, therefore not a set.
View attachment 9462
The Graveyard is the only building that has previously used the upgrades where the function does not change.
Maypole- At level 2 you get a coin boost, level 3 a larger coin boost
Cider Mill- A production building, but the options start at supplies only (maybe coins, too) and go through 1, 2, and 3 FP options.
There is nothing that can be proven here either way. There aren't any facts in dispute. This discussion is just bizarre.
By the way, one is a number, so one item can be a set. This is standard mathematics. You can, in fact, have a set with one element in it.
Can we back up and look at the point instead of odd sematics:
They are experimenting with event prizes:
* Confectionary/Graveyard would upgrade to bigger versions of themselves, but their function does not really change, so that's a bit boring.
* They tried to do upgrades with the maypole, but that wasn't very exciting either.
* They tried set buildings, but then you had to upgrade each one.
* Then they tried the cider mill, which was a bit better (from what I can tell -- I didn't build mine).
* Now, they are trying buildings with a large number of upgrades (7 levels) with the Pillar of Heroes and the Grand Bridge. As you win more prizes, you can upgrade it more and more and it improves (like maypole or a set building), but it goes further than a maypole (more levels), and you can motivate it, and you only need a single kit to advance it to the following era.
So, I do believe that they are feeling around and trying to figure out what makes for good event rewards (not horribly suprising that they would do so), and this is them trying to combine previous ideas into a slightly different form, even if the elements are not unique. Now the problem they are having with the Grand Bridge is that not everyone can upgrade it to maximum, and some people are unhappy about that.