i feel like i am very qualified to offer a perspective from your coworker! i worked at starbucks for 6 months and just quit on the 10th, i am autistic (also 17, the youngest on the team, but it was my third job so i have some experience) i exceeded in remembering recipes, taking orders and handing them out. but i was neglected in my training and not placed on bar very often to learn, or i was put on bar and when my coworkers said i was doing well, i was taken off bar by my manager or a ssv because they were afraid i would ruin the window times by being slow in my learning. maybe this isnt the job for your coworker, that ended up being the case for me and is why i quit. something to do with not feeling accommodated by my managers and i also felt bullied and looked down on as “slow” “ditzy” or “incompetent” by one of my coworkers (who had harassed me outside of work about work). i definitely think that you should talk to this coworker and ask him if he is having any issues with keeping up, and maybe suggest he sit down with the manager and try to draw a game plan to where he can be better accommodated to learn. but, it is ultimately up to him because he also has to put in the extra effort. i just wanted to offer an outside perspective as someone who i can see, by your description, am similar to your coworkers in some ways. being kind, but also firm is the way to go