I noticed that the game has some quirky behavior when started under "memory pressure" conditions. On my humble 8GB of ram, in normal conditions and with the lowest settings in 1080p, my physical RAM usage as reported in afterburner is just north of 7GB (which probably sets you around 5-6GB just for the game once the OS is taken into account.. unfortunately I didn't specifically check that)
But I left firefox open once, which was stealing a good additional 2GB, and you could very much feel how important those were for smoothness every time you zoomed out in the map. I then proceeded to close the browser.. And to my dismay stuttering was still going on and total ram usage wasn't going past 6GB. And I had to restart the game to get all my RAM used, and back to my solid 40FPS.
Also fun fact, contrarily to steam where you can play just forever once the free weekend expires if you had the game already running, Ubisoft just leaves you a 15 minutes grace period.