The horizontal tails being thin and oriented more or less radially from the exhaust plume, I don't see much shielding of the exhaust & plume IR signatures except from a front aspect, which is pretty much the same for most all fighters.

But through the several evolutions it's gone through, right up to the MiG-35, the tail design hasn't changed, and the Russians are known for keeping things simple wherever possible, so there has to be an advantage or constraint that keeps it that way?