More K-28 Thoughts

The thread on the K-28 photos got me to thinking about why the Grande sold 7 K-28 class locomotives to the government during World War II. After giving it some thought I came up with this rationalle.
Class K-28 was always listed in the Rio Grande's timetables as being PASSENGER power. Up to 1941 (or so) the breakdown was this...three locomotives assigned to Shavano service, three locomotives assigned to Chili Line service and three locomotives assigned to San Juan service (this works out to one locomotive running each way, with a third locomotive as a spare). The tenth locomotive would be usually in the shop.
By 1942, the Shavano and the Chili Line were history, making their assigned locomotives surplus. My guess is that by this time the remaining K-27's were mainly used for switching and light road duties by this time and were more suitable for this service than the K-28's were (during this period the Silverton mixed was being powered by the 375, and it (and the 463) were sufficient to handle the traffic on the Silverton branch), which made the remaining 7 K-28's surplus.
Why were 473, 476 and 478 saved? (assuming I got the numbers right...) Most likely these were the three most recently shopped engines on the property.
Anybody else out there have any comments?
Incidently, for the record, my absolute favorite shot of a K-28 is a Richard B. Jackson shot of the 475 running on the Chili Line with a train...absolutely terrific! I think this shot was published in the Chili Line book the Colorado Railroad Museum published some years ago.