Okay, so it was intended, good to know
I can understand why it would be difficult to design a level around it: if the player "misses the window" of the mid-air freeze, he could be stuck. Maybe some boxes would need to be fully stopped to be linked, and another type of items/box could be while in motion? I'm not sure...
The current levels are great though, so maybe such mechanic isn't necessary after all.
Thanks for the answer!