Think Martinez hasn't put him back in yet to prove a point. Wants to make sure Distin gets the message that you can't behave the way he apparently did and then just come straight back in.
They may have made up but what sort of message is it if you can F off and have a sulk (after rightfully being bollocked) but then come straight back into the side after just an apology? He probably wants to see Distin working hard in training to make up for walking out and to show he truly does want to get back to his best. If Distin had come straight back in then in his head he'd probably have felt justified for walking out or whatever.
Alcaraz is out for a while and I think he'll go the way Kone, wouldn't surprised if he never plays for us again now. Hopefully Distin has showed Roberto what he wants to see in training and he feels he's made his point. Distin and Jagielka, when both are at their best, are still one cracking CB partnership.