Whichever vendor told you that obviously doesn't care about our cars enough to be worthy of your hard-earned cash, because they have no idea what they are talking about. The headlight housings are identical; do a little
and you'll see this has been discussed and was confirmed when the Twins first came to market. The only difference is on the BRZ the bumper covers the inboard corner of the light a little more than the 86/FR-S. But those parts you are talking about will fit just fine.