I still don’t think an actual SMS would be received.

SMS is old-school. That thing is going via the tower or it’s not going at all.

(This is just a hunch. Happy to be told I’m wrong!)

My understanding is that "WiFi Calling" involves having your phone set up an IPsec tunnel (authenticated by your SIM) with your carrier, and then transferring essentially the same packets over that as would be transferred to the cell tower. I think that includes SMS traffic along with everything else.

(IIRC, the 3G and LTE versions of the tunnel carry traffic at different layers of the protocol stack, but in both cases being able to handle SMS and similar non-Internet features is part of the goal. As is being able to handoff between wifi and cellular transports in the middle of a call — I have no idea how well that works in practice.)

SMS will be received. It is just like being on the normal cell network.