The -main-is option to GHC should probably change the export list for the default module header. It doesn't.

$ cat Main.hs
program = return ()
$ ghc -main-is Main.program Main.hs 
[1 of 1] Compiling Main             ( Main.hs, Main.o )

Main.hs:1:1: error:
    Not in scope: ‘main’
    Perhaps you meant ‘min’ (imported from Prelude)

Main.hs:1:1: error:
    The main IO action ‘program’ is not exported by module ‘Main’

I cannot imagine any possible use case for a feature that changes the entry point name to something else, and then deliberately fails to export the symbol by that name. This seems like an obvious thing to fix.