Thank you for trying it! I really want some feedback before publishing it.
It’s a feature, called “scale snap”, that can be turned on and off, as you want.
Basically, there is a parameter that enables or disables it per axis. It can be specified as a global, or per connection point, so you can say ‘I want cubes scale to match the other side, but the pipes should keep their original scale’. Now the scale is something kinda tricky in UE, always local, so use with care!
There is also rotation snap that works the same way, you can specify it globally or per snap point, for each axis. By default Y,Z are fixed and X snaps at 90° increments, so for example if you try to connect the bend pipe to another one you have 4 possible rotations that will work. You can also disable it and just snap locations keeping the original rotation of the mesh.
Let me know if you have other questions, so I know what I should explain when I do documentation.