This is kinda strange. For fun I encoded an album at three different Lame 3.90.3 rates.
--alt-preset standard
--alt-preset extreme
--alt-preset insane


The last two tracks on the album puzzled me because the file sizes for the standard and insane encodes were exactly the same but the extreme file was actually smaller than both of them.

One of the tracks in question was "Show of Hands" from "Cat 'n' Mouse" by John Abercrombie on ECM it has a 9:18 duration.

File size for --alt-preset standard = 21.2 MB
--alt-preset extreme = 16.5 MB
--alt-preset insane = 21.2 MB

I would never have expected the extreme setting to be less than standard.

Anyone have any clues what is going on here?

Thanks!

Looks more like a mixup of command lines and/or files to me. I suggest you try to reencode.

Well, I tried again and things are now as I would have expected. Something must have got goofed up during my -aps run the first time. Oh well.