For 35 mm the gray tint of the layer has quite good antihalation properties itself, same principle as with the Kentmere films, but imo slightly better. It doesn't matter mostly and a halation effect can be seen maybe around strong lights, especially with night shots.
Because of the extreme high yellow-red sensitivity (see data sheet) of the Foma films you may notice highlight burning especially with portraits. This effect is different from halation. Although high red sensitivity reduces skin irritations the film makes a very pale skin. That can be what you want, but that's why I don't like the Fomas for portraits. Even a superpan film like Technical Pan makes much nicer skin tones imo, the colour range is extended but does not increase in red sensitivity. For landscape I like the Fomas.
Best - Reinhold