I think it's a mistake to think that all or even most high elevation lakes in the Sierra Nevada are all similar -- they are not.
In my experience (such as it is), how well a mountain lake fishes depends on many factors and can be quite different depending on the time of year, underwater topography, and a whole host of other factors that I probably don't comprehend.
One time I went to fish a lake in the Carson-Iceberg in the autumn around 9100'. A few years prior the brookies had been gangbusters, but this time not so much. Turns out from Google search I found a blog entry from a guy who had hauled in a kayak and spent a few days bait fishing it earlier in the year. Hah !
This summer on the other hand I visited a lake in Yosemite on the way to another that I knew fished well. The lake in question had supposedly been gill-netted and was now fishless. Except for all the rainbows in it, some pretty large ones, too.
There is a big lake ~11000' over a pass from Mammoth that has nice fat rainbows and apparently has for many years. No trail goes there. When I've visited in July/August the fish smack ed hoppers hard, but you have to go where they are ... it looks barren, but it's not.
Sometimes exploration is like that; sometimes you hit the jackpot and other times you just have to relax and enjoy a nice sunset
I've certainly been skunked before and I will be again.