> This behaviour is the same regardless of how long I wait after pressing esc.

Are you saying that no matter how long you wait, you never see "ESC-"
in the echo area?  If so, what version of Emacs do you have?

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No,  I'm saying even if I see ESC- in the echo area,  C-g still results in C-M-g is undefined.

Version = GNU Emacs 24.5.1