Hello Sean
With the topology that you have shared, it wouldn’t make sense to employ L2TPv3. Since you are using switches here, you would simply create a trunk and span the VLANs to the TEST-Warehouse switch.
L2TPv3 comes into play if you have a Layer 3 network composed of several routers, and you want to tunnel Layer 2 traffic over that. Something like this:
(TEST-CORE-SW) -------(R1) -----[LAYER 3 NW FABRIC] -----(R2) -----(TEST-Warehouse-SW)
The L2TPv3 would be configured on the ports on R1 and R2, such that those ports would tunnel your L2 traffic across the Layer 3 network fabric. Does that make sense?
I hope this has been helpful!
Laz