Hmm, I could see a use for both the 1-IN-3-OUT and the 3-IN-1-OUT. First, one XLR DAC to rule them all! That is feeding multiple amps from the same DAC, which in my case means I could also control the volume of each with the single remote of my DAC.
Second, feed in each amp to the switch with a single out to my headphone, allowing quick and easy amp switching without cable moving. Could be fun.
Ah for me it would be similar, an SU-8 and a Monolith 887, Loxjie P20, and eventually a Glenn OTL. Though for me, no SE connections to deal with.