Googling it provides a quick-answer box that states this claim and provides a source:

https://www.google.com/search?q=what+percent+of+student+loan...

92% Federal student loans make up the vast majority of American education debt—about 92% of all outstanding student loans is federal debt. The federal student loan portfolio currently totals more than $1.6 trillion, owed by about 43 million borrowers.

I think it's then pretty fair game for a forum comment to then suggest there's a causal relationship between "an entity that can print the currency that denominates the debt is backing the debt" and "this drives the price of the thing up due to easier access to funding for it".