@Dave77
The following is a suggested wiring diagram for the Fibaro Dimmer2 (current) model when used in a staircase implementation. It is from a UK reseller so I cannot comment as to whether this approach is appropriate for US houses.
As you can see only one Fibaro module is required and both switches would be 3-way momentary aka retractive switches. The same article also shows using 3 (or more) switches on the same staircase circuit.
Typically the micro modules are fitted in the ceiling here in the UK because fitting even one behind a wall plate is a tight fit and multiple ones (for multiple light circuits) pretty much impossible.
With all US manufacturers having utterly failed to produce wired smart switches for the rest of the world, using a micro module like Fibaro with momentary/retractive switches is pretty much the only effective option here in Europe.