I'm not sure if I share your experience with time perception and stimulants. IME if you're on a stimulant and are forced to sit through a boring lecture, it actually feels longer than it normally would be. The key here is getting into a state of flow, getting full immersed into an activity that is interesting and satisfying to you, perhaps stimulants can promote this, but still it has to be something you like doing. I myself had many negative experiences on stimulants with a lot of stress when my focus was definitely much worse than it normally is, but I'm sure this has a lot to do with personal predisposition towards stress and anxiety. I usually perform much better on a anxiolytic, e.g. opioids in moderate doses always made me more focused and calm during activities I enjoy.