Thanks for the very competent replies so fast. Many issues bring concern when a little experience can alleviate fears. So the purpose of those pillars was that they were the OE guides, just a hole bored in the raw cast-iron, just like the cylinders. In a "valve job", they bore a larger hole and press in separate tubes as guides, similar to sleeving a cylinder. That leaves the walls of the OE guide thin and easy to break as the new guide is forced in. Seems they don't know that until it cracks and hard to backup at that point, so some shops just leave as is.
Perhaps they could first mill down all the pillars. That appears to be how aluminum heads are cast, without pillars, since they use separate iron guides from the start; but would be more costly and this was a very active shop. I was surprised how inexpensive this valve job had been, ~$90/head, which included repairing a few small cracks.
