It's soviet-era legislation, which is in effect in Russia also (Russia just officially doesn't have war). The fact that it is not repealed (because there isn't really enough public support) simply shows that Ukraine isn't particularly socially developed. Men, regardless of anything, are expected to defend the motherland, just like in Russia and just how it was in soviet times. This is normal for a country 30 years into democracy attempts.
Also, everyone knows Ukraine's losses are comparable to Russian. "If they knew the number they would surrender", by that logic, Russians would surrender too, right? Since neither side publishes numbers?