Does this stem from the rush to build leaner more "tree hugger" engines?
I don’t think so, I think it’s cost.
Iirc the problem is the same as the one that existed on the 5 cylinder ST of the previous generation. Namely that the engines are open deck (cheaper to build) but the cylinder liners lack stability compared to a closed/semi-closed deck design.
Unfortunately as ford have found out, running these engines in higher states of tune means the lack of support at the mating face between the liners and the head can give you movement. This is probably what’s giving the coolant loss. Cracked liners on the 5 cylinder are not rare either!
Sadly, I doubt either of ford’s sticking plasters will address the underlying issue.