I think the implication is that if estate taxes are high, then when someone dies their estate is calculated as hard assets + cash and they have to split that so

I think the implication is that if estate taxes are high, then when someone dies their estate is calculated as hard assets + cash and they have to split that somehow to pay the tax. If taxes were 25% and the house was worth 200k and the deceased had 20k in cash, you'd end up paying 55k in taxes but only have 20k in cash to pay it with unless the descendants used their own funds. As such, it's easier to sell the house, take the 220k and pay the taxes.