Well “Graduation Leis” are listed on the Party City “party essentials” site:
So its clear they are synonymous to some degree.
But it never occurred to me it wasn’t completely universal in the US (as I’ve attended a pretty wide sample of different types on graduation in different bits of the US, albeit geographically centered on the SF Bay Area and DC). Those who have never seen them, how recent are we talking about? Most of my mine have been friends college/grad-school graduation or their kids high school graduations, in the last 5-10 years.