All true, except the bit about the loans not incurring interest until after graduation which is true only for subsidized federal loans, not for unsubsidized federal loans or most private loans. But on the other hand, there’s nothing to prevent parents (or grandparents) from helping the graduate repay “student” loans, and my guess is that a fairly high percentage of middle- and upper-middle class families do provide this kind of help, either at the beginning of the loan repayment period while the newly minted graduate is still looking for work or just trying to get established financially, or by paying the interest on unsubsidized loans during college to prevent accrued interest from being added to the principal that needs to be repaid once the repayment period begins, or by stepping in as an emergency funding source if the graduate has a career reversal or unexpectedly large medical or other expenses, etc. There are even some undisclosed number of parents like me & DW who choose to repay the “student” loan in full out of their own pockets, in effect treating the low-interest “student” loan as a convenient and financially sound way for the parents to spread the high cost of a 4-year college education over 5 or 6 years. We could have done this with a Parent PLUS loan, but the interest rates on “parent” loans are much higher than those on “student” loans.
For all these reasons, it’s a lot less scary and and lot less risky for a middle- or upper-middle-class kid to take out $30K in “student” loans, knowing that her family “has her back” financially. Borrowers from low-income families don’t have that same kind of backup.