For the scientists it was 5 years, for Wanda it was much shorter. She fades in Infinity War, comes back and fights Thanos in Endgame, and then finds out Vision is disassembled and being tested on.  Wandavision is set 3 weeks after the end of Endgame, so we are seeing fresh wounds.

In other comic plots the twins were birthed of pure multidimensional energy that Wanda was able to use to create them. This is the story where Harkness and Mephisto take them, but they could be taking a little from here and a litter from there to build a new MCU plot line.

It’s even better when they zoom out and you see that she has been sitting across from him and somehow didn’t just start laughing at the faces he was making.