Here is a link from an official source with the news featuring a direct quote from Activision
https://www.google.com/amp/www.playstationlifestyle.net/2018/08/01/spyro-reignited-trilogy-download-disc/amp/
It seems to be the case that if you buy the physical copy of Spyro (regardless of console) only the first game is actually on the disc.
Games 2 and 3 require downloading. Naturally i've seen a lot of angry people and it may mean buying the trilogy preowned at a later date would only net you...