This isn't entirely true.
You do have a 6 month grace period before repayment is expected. And the terms of federal loans are usually independent of who the signer is (yourself or your parents).
The deferral point is incorrect, but this is partly a semantics issue. President Bush signed a new law a couple years ago that removed the ability for medical students to defer their federal loans during residency (Thank you Mr. Bush). The only options currently available (without refinancing your loans) are to begin making payments or go into forbearance. And even with refinancing, rarely can you get a deal that is as good as the old deferral option was.
Deferral vs Forbearance:
Deferral - the loan amount eligible for deferral would sit idle and not accrue interest during residency. This option obviously saves money.
Forbearance - the entire loan amount continues to accrue interest, though no payments are necessary for the forbearance period. You actually pay more for the total life of the loan, than if you started paying right away.
Most of this applies to federal loans, which are responsible for >95% of the loans used for medical school.
-senior medical student / admissions committee interview