The difference in lengths is probably the tongue. I think Forest River lists the total length of the trailer in their stats. If the present owner just measured the living area, then through in the bumper and tongue, and that might be pretty close to the 25'10".
I am hitting a dead end on NADA. It appears that they only list Midwest/East coast models, and the T23FBL is a Pacific Northwest model.
Chap , DW Joy, and Fur Baby Sango
2017 F350 Lariat CCSB, SRW, 4x4, 6.7 PS
2017 Grand Design Reflection 337RLS