Hmm, not too sure you've got the right plant name, as you've mentioned pulling off "bottom" leaves, sounds more like a Cordyline (with a trunk and growth at the top) rather than Phormium (no trunk, all growing from the soil). assuming it is cordyline, yes, you can take off the dead leaves.

I take the "bottom" leaves off my phormiums as they are always the ones that are old and withered and lie on the ground.
If they are very old, I can just pull them off instead of cutting them.