*Most* of the time ...
I define "squaring up a block" as using an actual ruler to make sure that the finished size is accurate. And most of the time yes, I square them up.
But the quilt I'm currently working on has 221 4.5" blocks. Am I going to take each one of these and plop them down on my 4.5" square ruler and square them up?? Probably not. I will probably *eye-ball* each of them as I am joining them to see if I need to fudge a seam. I'll join them in units of 4 and THEN I'll square them up with a ruler, then I'll join 4 of those units and square that up ... etc. Bear in mind with this quilt I am making 111 of one block and 110 of another - so I'm making 40 or 50 blocks at a time all chain pieced. So no, I am not stopping to square up each little block.
If I were making 200+ Dear Jane blocks ... I'd be making ONE block at a time and yes I would square each one up.