Happened across a website "Robs Plants" that has an in depth article on cranesbill geraniums. Shows a huge grouping of leaves and how they differ from one another. You might get your answer there. Happy Gardening!

I've had my Cranesbill seed it'self and the new seedlings have that closed leaf. As the plant matures the leaf splits like your established plant. Both are definitely sanguineum geranium leafs. I'd say your plant is a young one that has not yet developed the split leaf