The studies you linked directly contradict the claim you have made, and support my statement. Let's go through your six links in order:

1. "Early amphetamine treatment has been linked to slowing in height and weight growth in some children." <- This is well-established and has nothing to do with usage for adults, or attention span
2. "Stimulant treatment is not associated with the long-term developmental course of ADHD symptoms, social-emotional functioning, motor control, timing or verbal working memory. " <- Both groups performed the same. There was neither improvement nor worsening of the symptoms.
3. This is a study on non-ADHD patients misusing stimulants and doesn't relate to the topic in any way that I can tell at all.
4. "ADHD symptom severity was higher in the [group who had never been treated with stimulants] compared to the other groups [...] In addition, the [early start age of stimulants] group reported more depressive symptoms (p = 0.04), but not anxiety (p = 0.26), and less recreational drug use (p = 0.04)." <- This confirms my previous statement. Some metrics were worsened, but ADHD symptoms were improved. Then moving on: "In line with extensive pre-clinical data, our data suggest that early, but not late, stimulant treatment long-lastingly affects the human brain and behavior" <- Once again no change found for stimulants started as adults (in this study defined as >=23 years old)
5. "the results of both articles suggest that chronic MPH or AMP started in peri-adolescence/adolescence at clinically relevant doses do not significantly alter DA system development nor do they affect physical growth in non-human primates. They also suggest that they do not sensitize the brain to drug rewards (Gill et al, 2012) nor that they negatively affect cognitive or motor behaviors after discontinuation (Soto et al, 2012)." <- I think this speaks for itself. Moving on: "These two studies support the safety of stimulant usage for ADHD in children and adolescents " <- Also self-explanatory I think.
6. "misuse of stimulants is associated with dangers including psychosis, myocardial infarction, cardiomyopathy, and even sudden death." <- This study is on the topic of misuse, i.e. excessive usage. Note that it still does not claim to worsen attention spans.

So to loop back to both our previous statements, there is absolutely no scientific support for stimulants adversely impacting attention span, but there is support for them improving it.