Subarus were having head gasket problems 30 years ago and then as now, Subaru denied there was ever a problem. Subaru even had a service bulletin issued way back when stating there was not a problem with their head gaskets (marketing dept. at work) but would cover them “if the customer squawked enough”. Not phrased like that but you get the point.
JMHO here, but I feel the problem is a bit deeper than head gasket design. They’re using 6 head bolts per side as compared to the earlier (and generally trouble free) 8 bolt design.
Another factor is lack or a head bolt retorque at a very low mileage. In theory torque to yield bolts should not be retorqued. In practice it may be a different matter since every metal known to man changes its shape over time.