The Ukrainians definitely know what they are doing. I think the video I posted yesterday talks about that river and how UKR had stopped them once before but that RU was going to have to try again because it's important.
There is a thread on twitter of the UA soldier who is also an engineer and was tasked on identifying , if RF forces WERE to cross, where they would do it.
According to the thread, he nailed it. The UA forces prepped for this before hand.