Using foam-board construction adhesive works well long-term between the sub-floor and foam, but the bond to the concrete may eventually give up in time, depending on the moisture content of the concrete, and the shrinkage rate of the foam. (XPS will likely have a bigger issue than EPS here.) Many solvents will degrade foam, so sticking with the purpose-made adhesives is advisable. Moisture changes in the plywood can also cause upward forces, pulling away from the concrete forming "waves" in the floor. But if the slab has a poly vapor barrier the risk of breaking that foam/concrete bond is lower, since the moisture content of the concrete will be less, and the humidity stresses causing the wood to curl are lower.

A half-inch of foam isn't much of a thermal break against the +10C subsoil of Vancouver.