You are exactly right. The bee takes the easy route. She's not a pollinator, just an egg layer, and puncturing the flower gives her the nectar to sustain life. I've seen Orioles do the same thing on a trumpet vine. I'm not sure exactly what type of bee it is, but I keep mason bees, and they're very different to honey bees. And "your" bee is not a honey bee!
RE: Carpenter Bee Feeding From Unusual Place - Mexican Petunia