Karma coming to visit the Russians? Ukraine ought to take responsibility. And then a dozen western countries too. Probably the wrong thing to do but it would feel good for a moment. ;)
No, Ukraine certainly prefers plausible deniability here.
The "fire season" is also beginning right when Mariupol is about to fall with many thousand people, the majority of whom could be described as having been taken as hostages, surrounded by the Russian with troops ready for slaughter.
Do not underestimate the significance the events around Mariupol have for the Ukrainians.
THe Russians know this as evidenced by Putin personally stopping the final assault on the last redoubt of the Ukrainian forces and thousands of civilians in Mariupol.
The Ukrainian government has also made no doubt about that there is a red line about to be crossed in Mariupol.
This comes at a politically difficult time for Putin and he has no way to predict how hard the Ukrainians could hit soft targets in Russia.