To be honest the cpu plate approach is the same whether it's rookie or legend. Same with how they pitch. They will paint corners or rookie just the same as they do on legend. Only thing difficulty setting does is increase or decrease the size of the PCI. It's simply a placebo effect imo if you think the cpu is more patient at the plate the higher the difficulty. Discipline is a player by player attribute. Some players will be more disciplined and others will not. Just my opinion from my experience up and down all difficulties.
As far as the contact slider goes...the higher it is the better their timing is, thus more contact and better contact is made. The lower the slider the worse their timing is so they make less contact, and weaker contact at times. Also the lower it is they will be called for strike check swings rather than an actual check swing. If you put it on 1 or 0 it's nearly always called strikes on check swings. That's the only place where the discipline comes into effect with the contact slider from what I can tell.
You're getting strikeouts due to their smaller PCI rather than contact slider at 6. They will chase pitches a lot no matter the pitching difficulty setting. Again all my opinion from my experience playing through all the different difficulty settings. I've taken pics of PCI during same at bat on different levels and with contact slider at 0 and 10. It's always the same size until you change the difficulty setting.