Maybe because the commander already combines good abilities like the T-34/85 (top main battle tank) /Shock troops (top doctrinal infatry)/Strong off map (very cost efficient thought a bit inconstant)/120mm mortar so the remaining ability should be less potent else it would run the risk of overshadowing other T-34/85 commander reducing the number of meta commanders.
The aim of commander patch should not be to create the commander with best abilities but to bring as many commander as possible to similar power levels.
I do think he meant that Vehicle detection has absolutely no thematic fit in Shock Army. There are other less powerful abilities which could have been taken instead of Vehicle detection.