Sure it might look familiar, but there is a different intent.
YES. The first time this was evident to me was when some friends of mine who practice Chen Tai Chi were showing me their basic stance. I was struck by how they "tucked" their tailbones, similar to what I did when I was studying karate. But in karate, I was told to pull the pelvis up with the abs
. But my friends explained that they were relaxing the lower back downwards
Looked almost the same, but totally different feeling.