Using the fare finder on this site will tell you that the Notting Hill Gate fare covers zones 2 to 6 and the Paddington fare covers zones 1 to 6.
I don’t think you’ll ever see an ‘Avoiding zone 1’ caption on a fare that starts in zone 2 (effectively) and travels outwards. For the route via Paddington, my limited understanding of OSIs and the fact that fare finder doesn’t display a different “change at Paddington” fare suggests that the zone 2 to 6 fare might also be charged via that route. The alternative is charging separate fares from NH Gate to Paddington and then Paddington to the airport which is unlikely.