I don’t know whether Boris has an SEO expert on his team but this appears to be a successful piece of search engine “optimisation” which is to say nerfing.
nerf (verb) : To weaken, especially of weapons in a computer game. After the company making soft-toy weapons.
Googling Boris bus has, since 2016, produced images of Boris Johnson and the Brexit bus, bearing the lie about the UK sending £350million per week to the EU.
Whereas when Boris talked about painting model buses in an interview on 25th June 2019, the flurry of internet comment it caused led to searches for Boris bus producing results for the interview instead.
I have no idea whether Boris does paint model buses, though I do know he tells lies. Eddie Mair’s interview of Boris is remarkable.