As the title says, is it correct? Thanks
Global variables declared in Design > Templates > Global Variables cannot contain EE tags, PHP, or other variables inside them.
User-defined global variables are not run through the template engine, so you cannot place EE Tags, PHP, or variables inside them.
If you need to place EE tags inside re-usable bits of code then you'll need to use Snippets: Design > Templates > Snippets. They're parsed at a very early stage of template rendering so can contain dynamic variables.