Linux

Both of your conclusions are incorrect.

Whether the command is a built-in or not will not affect the result of the variable assignment.

grep does not interpret those double quotes because grep never even sees them.

You really should read the man pages I linked in an earlier post. Everything that you are trying to deduce is spelled out clearly.

Regards,
Alister

Whenever you're confused as to the result of a string expansion, shove it into echo and see what it does.

Code:

$ echo a

a

$ echo "a"

a

$ echo 'a'

a

$ echo "'a'"

'a'

$

If you manage to actually give a quote to echo, it sees it, but outer quotes are stripped by the shell.