Do you mean that a left-turn is not allowed here in real life, or that some sort of routing service doesn't allow one here?

If the latter, which service? The ones hosted on osm.org seem to work, for example: https://www.openstreetmap.org/directions?engine=graphhopper_car&route=43.33996%2C-79.81588%3B43.33781%2C-79.81629#map=19/43.33889/-79.81661