Dont the 402 still accept oyster cards?
No. Paper One Day Travelcards are accepted between Bromley and Knockholt (I think this is for historical reasons, connected with Knockholt having been in LB Bromley until 1969), but Oyster cards are not.
I'm not sure if it's still the case, but last time I used the 402 Oyster holders could travel for child fares (Knockholt to Bromley £1.30 instead of £2.60, iirc), but they had to pay that reduced fare in money.
At least it's clear to passengers that this is not a "normal" TfL service, because Arriva-coloured buses are used rather than TfL-coloured buses. Arriva-coloured buses are also used on the 477 (Orpington - Swanley - Bluewater), which also doesn't accept Oyster cards.
It may be less clear to passengers at Barnet embarking on a Metroline 84 towards Potters Bar and St Albans (and now Luton, but it certainly didn't go there "in my day"!). Oyster cards used to be accepted between Barnet and Potters Bar but no longer, and yet the bus is still red.