Because like pdeaves points out, if they are now tri-modes, then they were bi-modes as they left the factory, which is clearly nonsense and contradicts Porterbrook's marketing that they're being turned into bi-modes in the basic 769 form!
Just because you can work something backwards doesn’t mean it’s necessary to, they have three discrete modes of operating, each with its own driving characteristics with its own training requirements. It is still a valid description simply by being the chosen brand by the person supplying the product, Technicality doesn’t come into it. You could quite easily say that all trains have one mode, wheels rolling on a rail, but then you could also say every train has 2 modes, wheels rolling one way and wheels rolling the other. It makes absolutely no difference whether you choose to fight the corner ‘dual voltage bi mode’ or ‘tri mode’.
apologies if this comes across as me being an arse, I just get annoyed with pedantry for the sake of pedantry, if something needs explaining, fine, but it’a a pretty clear description whatever way you say it. Potatoes potatoes