Some Schneurle ported engines, namely MDS and others, do not run well without an idle bar glow plug. The Schneurle ports in such engines are (wrongfully) angled in a way that dowses the glow plug with raw fuel.

A classic Schneurle porting only has the side ports, angled away from the exhaust port.
The boost port is an addition that further boosts power. Hence "Shneurle plus boost port..." term.