Suppose you bind a spell to shift+q, and that spell requires targeting ftl wise.

Then when you make the ftl macro's for your alts, they will always automatically see shift, as you are already physically pressing it.

So shift+q always maps to shift+whatever you map too.

ie. if you map shift+q to for example:
shift+ctrl+u as well as ctrl+u it wont work, as both will see shift.

And thus you have to adjust the ftl macro's to always include shift, since it is physically pressed.