So, if we have a 6.5/140/.287 SD bullet with the same SD as a 30/190/.286 SD bullet.
Both will penetrate the same then according to Buffalobob. Since both have the same SD.
Two bullets with the same sectional density but different masses will not penetrate the same on an animal. One only needs to consider a 17 caliber bullet striking a shoulder bone versus a 338 caliber bullet striking a shoulder bone (both with the same sectional density) to understand that there needs to be consideration of the mass involved in the impact.
One can examine a theoretical rifle that would fire a quarter (25 cent piece) either flat surface forward or edge forward to visualize that with the flat surface forward the quarter has low sectional density and will make a big raised welt but little else. If the quarter is instead fired edge forward then it will have higher sectional density and penetration will occur. So we see that the with the same mass, but different sectional densities, the penetration will change.
The interplay of mass and sectional density is something we should consider when selecting a bullet for a particular application.