Yeah... cover acts like big ol' sail.
When I was an apartment dweller, I kept my old 550LTD under a cover and it went over a few times. Once on a BRAND NEW cover... and the battery leaked
Between that, and having covers stolen (even with a lock through the grommets).... I'd taken to looping a cable around the bike, then locking to the grommets.
It was just long enough to reach all the way around, so it not only provided a visible deterrent to a quick-grab of the cover, but it also took a lot of the "sail" properties out of the cover by keeping it tight around the bike.
It also provided me with a nice long cable for looping through jacket sleeves and helmets to secure to the bike