They don't. They already admitted there are fatalities and POWs - without specifing the numbers, though. I can bring a link, but it would be in Russian.

 

The "no casualties" remark was about one specific combat action - the airborne assault near Kiev. However, it is, too, should be taken with a spoon of salt, because in the very same speech that general also said "200 helicopters" were used for this op, which I find incredibly hard to believe. I can get "200 helicopter sorties" but not 200 helicopters.