"The (strong) implication being that any WordPress configuration will perform better on WPEngine than on an alternative hosting platform."No, there's no inference or implication that any (ie regardless of how its built) WordPress configuration will scale on WP Engine. As I wrote in my prior comment, scalability is a partnership between infrastructure and code. That's the case irregardless of framework and PaaS provider.
We like car analogies at WP Engine - if I sell you a racing car and you're only a moderately good driver then you're going to crash when you approach the corner at 200mph. There's little I can do about that other than teach you to drive, and I'm in the business of building the cars. There are plenty of folks who can help you improve your race-craft out there.
To say that we've missled someone is an unfair assertion.
If I analyze the suggestions you're making in your comment here...
* Jacques complained about lack of 24/7 support, but I shouldn't have tried to reply and explain the reason for that because 'there's no crying in business'. ?????
* The WP Engine website shouldn't mention scaling WordPress because it's not technically possible to scale all WordPress code regardless of how it's written. (What should our site say? What should any scale-orientated PaaS website say given the same issues apply to anyone in this space)
* WP Engine should vet and screen it's customers so that they must prove their code can scale before we sell them an account? ?????
I'm sorry, but if that's the advice you're offering then, with respect, I don't agree.