The kind of moonflower seed you have is a datura. The give away here is the prickly pods. I think the larger seed you read about was the one in the morning glory family - Ipomoea alba.
As far as pulling out your plants and disturbing your bulbs, another option is to just cut the plants down to the ground in the fall and leave the soil undisturbed.

Yup - those are datura seeds - Moonflower aka Angel's Trumpets (so are Brugmasias, but... just shows that common names are common to different plants).

Datura do root deeply. They're perennial in my zone, might not be in yours though. But cutting them at ground level would work, It's what I do to mine in winter. Mine flower from June until first frost, with very large and very fragrant white flowers every night - one of my favorites!