I have no idea who the ATCO was but if it was a Lufthansa aircraft turning onto stand early then I would guess he was taxiing on to F6, F7 or F8 and when you say he turned onto stand a little bit early, what I suspect actually happened was he took the crossover from K onto Z without clearance to do so.
This may not seem like a big deal, but if, for example, we have cleared an aircraft to taxi to stand F6 via K, we expect that to happen and we can then push from F7 or F8 without worry. By taking the crossover without clearance, it then straight away creates a confliction that shouldn't have been there.
BA also have a habit of taking the crossover without clearance.