PSVAR only applies to the vehicles, not the infrastructure. It's following the letter of the law, not the spirit of the law.
The exact same can be said about Wellglades Yutong Flixbuses which serve Stand SB in Leicester, Stop 1 in Nottingham Broadmarsh, Stand B in Sheffield Meadowhall as any stand at Heathrow Central Bus Station. None of those are accessible for wheelchair lifts which are in the middle of the bus. But everyone gets away with it thanks to silly law makers who leave loopholes like this open, and poor regulators who make no attempt to ensure operators aren't actively choosing inaccessible stops/stops which would cause unacceptable delays or adjustments if a wheelchair user wished to board (Ie, Red Arrow).
While not specifically Red Arrow and Victoria Bus Station, I know an issue was raised with the traffic commissioners and local authorities about a very similar situation in another part of the country (operator using coaches but purposely serving inaccessible stops to avoid having to pick up wheelchair and less able passengers), the LA couldn't care less and said it's a free market, operators can do what they want. Traffic Commissioner gave nothing but their bog standard 'thank you we will pass it on'. There's no appetite to solve the situations.