You would see this consistent 30-40 min padding time for all flights. Long haul a bit different as it’s more effected by high wind speeds. So if BA would start flying from LHR-LGW the published block time would around 45-50 min. Not because BA wants to avoid from anything but push back and taxi time would be probably 30 min for both end plus some hold time.
delay compensation starts from around 3 hours so an hour delay won’t really make any difference. It is quite rare but happens sometimes that extra 5-10 min “missing” to claim.
BA also have to take into account connection times as most MAN passengers are connecting. So even if your MAN shuttle take off about one hour delayed it would probably be 30-40 min delayed by arrivals so most people even on tight connections would make it.