It's a common configuration - whether a snubber or a rigid support. This is the standard API 520 configuration... for local vents.

If it's a local vent, the transient effects are typically ignored and flow is assumed to be instantaneous.

If it's a remote vent, the transient effect is proportional to the lengths of piping runs between the silencer and relief valve. Loads at the silencer should take into account pressure losses in the piping, but if you want to be conservative, you don't have to.