Seems to me the T2500 equalled an R52 while the T2600 was similar to the R62! I remember inquiring with my White dealer at the time about the T2600; - he didn't seem too interested in following up, since he had been selling "against" Gleaner for years with the 9700's and 9720's!
You are correct. Except for engines and decals, they were identical. Seems I heard that most of the "White" Gleaners were redecaled to "Gleaner" Gleaners eventually.