Stihls are true 4 strokes. They just have a different oiling system. That would be like saying that an engine with a dry sump oiling system isn't a true 4 stroke because most 4 strokes use a wet sump oiling system...
It doesn't matter how the oiling is accomplished. To be a true 4 stroke an engine only needs to have 4 strokes in a power cycle which the Stihl engines do.
When did Dolmar come out with a new design. I know they have had a 4 stroke design for a while now.
Serving Greenville, Winterville and Ayden NC