SASLess
I agree with you, and if I had been the Russians I would also have blown it, as it narrows the potential offensive areas a little. However I do not believe the Ukrainian's would have advanced below that dam knowing the potential of it being blown, unless they had a plan to capture it beforehand, similar to the German strike on the Fort at Eben Emael prior to their move west in 1940. However those types of operation are fraught with risk, and I do not think the Ukrainian's ever planned to move below that dam while it was in Russian hands.
Cheers
Mr Mac