A positive step towards what? Effective coparenting? Reconcilliation?
I find when there is comfortable communication without tension it is positive for many reasons. It's good for your kids to see you guys communicate without discomfort or hostility. It's great he is wanting to spend more time with them. All this stuff is definitely a positive step towards the kids, no doubt.
As far as a positive step to wanting to work on the M again? I wouldn't put all my eggs in that basket. He was kind, take his kindness for face value. I say this not to dash hopes, there is no saying what the future holds......
But sometimes when we get out expectations up of a particular action, the fall from it is kind of hard and "undoes" some positive forward steps.
Maybe take this as an opportunity to contact him the next time if you aren't sure what time he is coming so you both don't go to pick up the kids when you don't have to.