Quite often I agree that they suggest planting too early for us. On the other hand, I have to remember that seeds planted very early might not germinate until they get warm enough. So you get the benefit of any early warmth for gain a few weeks. Only caveat would be if your weather tends to go up and down like a yoyo. And the poor seedlings get caught in a late frost. Course you can always use row or whatever works in your area.
I too am going to try planting seeds in my raised beds a bit earlier. I have hoops over top and will put poly over then to gain a bit more warmth. I am thinking around the middle of April for cold weather crops like lettuce, carrots& brocs etc. All the other stuff gets started indoors.
Stupid dahlias, lilies, crocus, daffys are trying to grow now. I brought the pots in from the garage and have them huddled next to the three aero gardens and two grow lamps to share the light. I should have the spring flowers wayyyy before the snow is even gone outside.