OK.. been toiling with this for years.

The other day, in Lowes, I spot 12" x 14" L-bracket shelf supports
rated at 100 lbs. So I figure 4 of those mounted to a 2x4, mounted to
my shop wall studs and spaced 12" vertically apart or so and that
should be adequate. I ran some calcs based on wood density and a
stack of 12" oak that is 10" wide would average out to less than 100#
per support.

oak 50#/cuft
50 x 8' x 12" x 10" / 4 supports = 83 # / support

What am I missing?

Mount several sets of 4 in-a-row and walla -- instanct lumber rack for
$2 a support ($8 per row)