For me, it depends on what I'm working on and what it looks like when I'm done FMQing.
I ALWAYS trim my quilts square before adding binding, and if it's really distorted from FMQ and is going to be a wall hanging, table topper or the like, I may soak and block it before trimming to ensure it will lay nicely, even after lots of use. If it's a bed quilt, sofa throw or lap quilt, I'll just trim it square and bind it. Then I wash it before using or gifting so it's ready for use.