Isofix is all about precisely defined dimensions on the fixings, meant to be common between all cars. Alfa does meet those dimensions and positioning, but haven't helped us because they've made the hole in the seat a tiny little slot and the metal fixings buried inside - but, persevere, and it will fit. I have an isofix forward-facing seat now for my youngest and hated pulling it in and out, its like wrestling a bear and the more of a rush you're in, the harder it seems to be. But, it will go in, and attaches firmly once done.
By contrast, my wife's C-Max has the isofix attachment points clearly exposed inside a little plastic socket each side. Takes mere seconds with no effort at all - how it should be, IMO.