Complete nonsense, flooding causes more problems for the attacker. That's why Soviets blew dams in WW2.
Second world war: Dnieper dam blown up by Russians – archive, 1941
Stalin’s secret police blew up the dam in an attempt to slow the advance of Nazi German troops as they swept through Soviet-era Ukraine
Blown up dam at Zaporizhzhia, 1941
Seriously, you actually believe flooding always causes more problems for the attacker?
LOL well no need to continue with that discussion, that is not how things work. I am no military tactician but know enough that flooding can favor either depending on troop positions, logistics/supply lines, timing to mention just a few things.
Might want to expand your understanding of such things.
Oh I might add, given Russia is actually the invader wouldn’t that mean, in your Example, Ukraine was more likely to blow up the damn form invading Russian troops? That is actually the WWII example you provide.