I need to correct my previous posts about the "cleverness" of Furman's SMP+ circuit. I shouldn't have relied on reviews and marketing materials saying the MOV was placed after the inductor.
Testing the board, it traces just like it's laid out. Both MOVs are completely unprotected by the series mode circuit. The 1st MOV is also before the over-voltage relay and has no thermal protection. So it's completely unprotected and not part of the LED notification circuit on the front of the unit.
How in the world they can claim that two (tiny) 120J MOVs placed before a small ferrite core inductor is "Non-sacrificial series mode surge protection" is beyond me. This also explains how the let-through voltage on the Wirecutter test was so low. The MOVs shunts most of the surge energy so the inductor only has to absorb a small surge.
So the first MOV could be fried and you'd get no indication that the protection is compromised. At least the second MOV has a thermal fuse and the over-voltage circuit, but it's still only one MOV. Both of those MOV's are taking the surge hit every time. It's an undersized MOV-based surge protector with a little series mode thrown in after the MOVs have done most of the work.
Compare the SMP inductor to the dual air-core inductors of a SurgeX unit and it's pretty clear it would get saturated quickly without the MOVs shunting the surge to neutral.
If you want an MOV-based surge protector, I would definitely skip the Furman and go with a Panamax. They use the same over-voltage protection with multiple layers of thermally fused MOVs connected to the protection indicator light.
Good thing I have a couple SurgeX units