That's indeed interesting.
I remember way back, hooking up my first guitar right into my audio interface and doing processing on the computer. I remember trying to record at like 10-12ms input latency (this was long before I understood buffer settings and so it was left in the default near-middle position) and feeling like it was unplayable.
Right now, I use a G10 Relay into the Helix, XLR out to Kemper, SPDIF back again, 1/4" out to two Strymon pedals and a rack compressor, back into the Helix a second time, then out to Powercabs through AES. In order to go from Kemper via SPDIF I have to use a box that translates SPDIF to AES, not sure if that has any inherent latency, but one should figure I had tons of latency in this rig. However, it's totally playable. There's no way I'm above 8ms latency. I haven't played straight into an amp in a while, but it feels like there is no actual latency, that's how tight it feels. So that's five rounds of AD/DA and any latency introduced by any of the four digital signal processors (five if you want to count the SPDIF/AES box) that are in line. That's just mindblowing to me. So in all actuality, it doesn't really matter. I don't mind when things are optimal, however.