The answers you get always depend on the questions you ask!

Again - read my lips! My example was not about spouses passing away but a friend, thus not a relative. Spouses fall under tax class II, as children above 21 do. Up to a personal capital of 402.678,11€ the factor applicable is 1,00, but as soon as this amounts raises to 4.020.770,98€ they also face a factor of 1,2. (§21 tax law).
Ofcourse it's not about immediately selling real estate to cover the tax load - as long that's not completed you're not the owner who would have the right to do that, i left out the trival step of a bridging financial operation.
And the timepoint with regard to the spanish german tax treaty is correct, Jan. 20th as far as i found out, but nothing has moved for 40 years and it just did not cover heirship.