Edit: My answer was written from memory and was incorrect. Front/rear split systems remain in use to this day, mainly for rear-wheel-drive vehicles.
Best advice is to consult the manual on brake bleed order. Even when you know how the system is split, some manufacturers recommend non-obvious orders for bleeding.
US vehicle regulations don't even specify that a hydraulic brake system must be split, much less how it must be split.
I assumed the advantages of a diagonal split would mean nobody'd still use a front/rear split, but that's not the case.
There are some cars with redundancy on the front axle (one circuit is front + left rear, the other is front +right rear), e.g. Volvo has been doing this since the late 1960s. Other options are one circuit for front, another for all 4 wheels, or 2 circuits that serve 4 wheels each (Rolls-Royce do this IIRC).