Arn't seeds perverse

[Primrose]

When I looked in my veggie patch this morning where I had spread last year's compost heap I found about 25 robust little endive seedlings growing and looking just as healthy as the salad leaves I sowed under cover. Since I didn't grow endive in that area last year, the seeds must have come from the compost spread during the winter and overwintered. I've known tomato seeds to survive in compost but think this is the first time I've had any salad leaves. Is this unusual?