The pot is an attenuator following on from the fixed output.

It is followed by a discrete unity gain buffer which drives the variable output.

At maximum pot setting, the output is the same as the fixed output.

The pot is an Alps 16mm carbon audio taper track, offering the least trouble, as these have been in use by us for 20 years or thereabouts, and have proved reliable.

A switched attenuator, on the other hand, relies on numerous switch contacts and several individually soldered joints, each possessing the equivalent of a thermocouple junction, like all transitions between metal types exhibit.

In audio, it is suggested that circuitry paths are kept as short as possible, but the reasons behind it seem to be long-forgotten. I shall not run through them here, but circuit complication is just as bad as unnecessarily long circuit paths.

Thank you! I've leaned that many amp designers set up their attenuators so you get unity at 12:00 or so because it is aesthetically where users have come to expect full volume. 

You're approach is exactly what I would have hoped for and expected. It has the added bonus of allowing attenuation to match so many cartridges that now have a pretty robust output—often more than is needed. That means that if I chose a different cartridge in the future I would be confident of being able to get a gain match. Gain matching has been one of those factors I've become increasingly aware of over the years. I often listen to Jazz recordings where a piano or horn player will come in a little hotter than the recording engineer anticipated. It's these moments where I hear gain issues, and why I've come to think that getting the gain spot on brings the perfect balance of life and energy.