Funnily enough it is actually true in the majority of cases. Many are built to face into slopes too -

Howth, Gaulstown, Ahaglaslin kinda faces more into the hill than away from it, Arderawinny faces a cliff face that is just 10m from it, Kilgraney, Altdrumman is built just 5 from a rock outcrop, Ballyquin faces the slope in front of it, Brennanstown faces up the valley which is actually west rather than the usual east, Taylorsgrange faces towards the hill next to it (again west instead of east), Garran, Ardabrone, The Labby Rock, Larch Hill, Onagh, Gortnavern, Ballyknock ....

How many more do you want?

Kiltiernan, Mayo in Cavan, Legananny and Browne's Hill are a few of the exceptions.