Master Builders: Illegal or Legal trick?

Hello!

I was exploring in newer versions when i noticed the saved toolbar section of the creative inventory.

If you have not played in newer versions recently, saved toolbars are hotbars you can load and save in creative mode. (added in 1.12)
So basically, I put blocks that can't be obtained in the creative inventory that work in 1.8.9 into these toolbars (barriers, command blocks, monster spawners) and then I loaded up 1.12.2 and went into master builders and I could obtain these blocks from my toolbar section.

So my question is: is this legal? Technically it is giving you items that other players may not have and giving you an advantage and it could also be called an exploit, but you cant remove Minecraft's features.

Possibly Mineplex could add something in the diamond that gives players access to these blocks if they are in a version lower than 1.12??

please leave ideas/replies!

 

I'm not sure, but that's resourceful.