Kern On

Latin T and Cyrillic Т & Ћ are in the same (left) kerning group – should I care?

Yes, this is intentional. Latin, Cyrillic and Greek will go into the same subtable, the other scripts will be separated.
Related: https://forum.glyphsapp.com/t/cyrillic-kerning/1286/23

Right, had forgotten about this. Thanks Tim.