I agree.
Measures I can see in the Photoshop dialog box are good.
Not need to auto resize anything.
In your print parameters, do you have something that automaticaly expand the image ?
I yes, you should disable it.
When you print image above through Photoshop, do you get 32,2cm and 27cm in output print ?
If you don't have A3 printer at home try with A4 version.