It's not FADEC.
In 1983 I had an XR3i which used the
Bosch K-Jetronic FI system. Started perfectly every time.
There were FI cars years before that, with no electronics in sight.
I think it is just the 1950s engine design, with fuel injection into the manifold, and no CHT-based fuel controls helping with warmup. It is fine in terms of specific fuel consumption, because one runs them at / near peak EGT in cruise and (assuming the ignition timing is about right
at that condition) that is as efficient as an engine is going to get, for a given compression ratio. I recall seeing an analysis done by an engine designer showing that those old engines are more efficient, at cruise power of say 65%, than any
petrol car engine made since.