These are the fitness rabbit holes I dive into...
It started with an interesting Short tidbit about sternum angle when bench pressing and how a steeper sternum angle means you're basically decline pressing when you're on a flat bench, then the longer video about it, then a sidebar video that sort of disputes much of it in terms of upper/lower chest gains, but also throws in tidbits about how arching your back matters to the angle in which you're pressing, too.
And it's nothing I stress out about or really even change in my routines, just find all the studies on biomechanics and so forth interesting.