Just because he knows that the Guardian only blocks the OP and not the TP, coupled with the fact that he's good Rand now doesn't mean that he doesn't have access to it at all. If anything wouldn't the DO want Rand to use the TP as much as possible since it will increase his chances of going dark again or going insane? To me he still has access but now knows better than to use it especially with the new memories or awareness that he has since TGS.