I am done with a chest of drawers built mostly out of 5 eight foot 1x12s from BORG except for the knobs - which I just ordered. It is in a room with a bed made of construction lumber from BORG. I think it is SYP. The legs are glued up into 3x3s. It is based upon a Matthias Wandel design. It is about a year old. Nothing bad has happened with it. It isn't used often but my kids like it when they visit. No cracking. No visible warping.

I worry less for about things for my shop than I do furniture my kids use. I would not hesitate to use construction lumber for a workbench - without waiting. I would not use badly warped pieces but a little warping will be eliminated when it is glued to other pieces. I would at least put it through the planner. Ideally a jointer first. To get a good flat surface to glue up.

Jay Bates made himself a workbench of pine and the same bench in hickory. He liked the pine one better. If you want inspiration you might want to watch his youtubes.