Yes, thrust line is a real thing. Just as real as a 5" longitudinal C.G. envelope
It needs to intersect the center of pressure (or center of drag as some may call it) at just the right place or be counter acted by lift (plus or minus) via an elevator. Reflexor as well in our case.
One of the many nice things about the high and low wing tandem-wing aircraft is that the engine is or can be between the two drag producing things (wings). I guess this is true for high and low wing bi-planes as well.
I think C-182 pilots know about the miss-alignment of the thrust line and the center of pressure. If it's trimmed for level cruise and you take away all of the throttle, the nose comes up hard and it take a lot of forward force on the yoke to keep it level. I learned/felt this in an Aeronca Sedan (O-360) for sure. Giant, draggy wing way up high with a constant speed prop.
