It was one of the reasons. Also, the minor matter of the aircraft being able to taxi to the gate.
As one of the people involved in the early technical discussions, I can assure you the
75m requirement at LHR came from the fire service. The aircraft could have been certificated to 0/0.
Taxying to the gate at Heathrow was facilitated by a combination of green centre-taxiway lights, ground movement radar and compass headings. The airline would have probably have liked something like 50m - although how practical that would have been for later wide-body aircraft is for others to say.