Hi Jbrussel93,
I think the people you've been talking too are presenting you with a parnoid world view.
There are two potential things to be suspcisious off (i) grade inflation, or (ii) a false transcript.
In the case of grade inflation, there are many other factors that come into consideration when evaluating prospective students that would mitigate this issue. These include the PGRE, reference letters, and even the student's ranking within each class. Every school/department has its own method for weighting each of these factors.
In the case of a forged transcript, it's highly likely that the student will be found out eventually, if not by the second set of transcripts that comes in when the student's undergraduate degree is awarded, then by any of the many exams required in graduate school. It's very likely that a forged transcript scenario ends poorly for the student.
In either case, an admissions committee is highly unlikely to red flag a 4.0 itself as "suspicious" unless there is some other evidence that would indicate that something odd might be going on.